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Analysis and Trends of Global Research on Nautical, Maritime and Marine Tourism

: Tourism related to the sea and boating activities is becoming increasingly popular and revolves around a range of leisure, water sports, nautical or other maritime activities. This article studies the main scientiﬁc contributions in this area, bearing in mind the complexity of ﬁnding a suitable deﬁnition of this concept. Hence, the aim of this paper is to analyze the scientiﬁc production from 1986 to 2020 in impact journals of the terms “nautical tourism”, “maritime tourism” and “marine tourism” considering the following variables: number of documents, number of articles, period being studied, Hirsch citations and index. The results show an increasing trend in terms of both the number of published articles and citations publications from 2007 onwards and the review of the literature raises the need to deﬁne a new concept: “blue tourism”. Future trends in research include terms such as tourist ports, quality of websites and blue economy.


Introduction
Despite the importance of maritime tourism in the local economic development of many countries, its dissemination in scientific journals has not followed a parallel development. Tourism has benefited from advances in scientific production, although the specific field of nautical tourism has scarcely been studied compared to the evolution of the broader tourism sector and its future perspectives [1].
In 1986, Miller published the first article on travel, tourism and marine affairs that analyzed tourism development policies and the opportunities for planning coastal tourism, highlighting some of the outstanding commercial facts of marine tourism, tourism management and the role of leisure, work and tourism in modern life [2]. Later, in 1989, an article on nautical tourism by Deskovic was published entitled "Marina development in Yugoslavia" in which the basic concepts of the development of this type of tourism and its viability were addressed [3].
Finding a single suitable definition that encompasses boating tourism, nauticalrecreational sports and marine activities at sea or in other aquatic environments is a difficult task and there are multiple combinations of words that refer to this type of tourism: nautical, maritime or marine. A decisive definition remains a complex issue due to the multifunctional nature of the activities related to the sea and maritime tourism. A decisive definition remains a complex issue due to the multifunctional nature of the activities related to the sea and maritime tourism. In the scientific literature in other languages, maritime tourism is defined in different ways and as a result there is no consensus on the part of the authors of a single general term that encompasses all its features. Therefore, as a prior step to the development of this work, the following words have been selected: nautical tourism, maritime tourism and marine tourism. These terms share conceptual similarities and, although there are features that are related to all the terms such as recreational activities which are related to coastal zones and the sea, "nautical tourism" is considered to be a 2 of 19 broader term that includes lakes, rivers and other aquatic environments where tourists can enjoy boating activities. Furthermore, there are authors who state that nautical tourism has not yet developed in rivers and lakes [4] and that recreational boating and its related tourist products are limited to the area of the sea coast. Once reviewed the contents of articles related to river tourism have not been taken into account for this analysis.
Marine tourism emerged as an indispensable issue in the field researching oceans and coastal areas. Orams [5] defines marine tourism as "those recreational activities that involve traveling away from one's place of residence and whose focus is the marine environment", referring to the latter as "those waters that are saline and affected by the tide". The definition also lists the activities that are related to it: scuba diving, snorkeling, windsurfing, fishing, watching sea mammals and seabirds, the cruise and ferry industry, all beach activities, sea kayaking, visits to coastal villages and fishing lighthouses, Maritime museums, sailing and motor boating, maritime events, Arctic and Antarctic tourism, etc.
According to Ecorys [6], maritime tourism refers to maritime activities such as boating, yachts, cruises, water sports, as well as its land services and infrastructure. Hall [7] states that maritime tourism is closely related to coastal tourism, but also includes all tourist activities derived from the sea, such as deep-sea fishing and cruises. At this point, cruise tourism cannot be included as a form of nautical tourism [8], because in this segment there is no direct relationship between the tourist and the sea, being excluded from this research. The main motivation of the cruises is not the realization of maritime or underwater sports activities, and the cruises act mainly as a means of transport, with multiple tourist services (accommodation, restaurants, shops, nightlife, etc.). Other authors state that cruise tourism is such an important activity that it should be studied separately, due to its magnitude and peculiarities [9]. Certainly, there are other documents that mention that this is a form of maritime tourism, but many others do not mention marine or "maritime" "nautical" terms [10].
The concept of maritime tourism includes all tourism activities related to the sea and the coasts. In addition to the use of pleasure boats and cruises, it includes a wide range of activities such as water skiing, windsurfing, underwater fishing, scuba diving, swimming and tours of marine parks [11].
The literature review covers numerous definitions of the concept being studied. Table 1 shows some definitions from the period 2000-2019 by various authors. It defines it as nautical activities, of a recreational or sporting nature, which take place in large bodies of water [15] Kovacic and Boskovic, Favro (2006) Nautical Tourism It is considered to be a recent commercial activity that has developed between ordinary tourism and maritime activity, comprising characteristics that make it a special type of tourism [16] Diakomihalis (2007) Marine Tourism Defines maritime tourism as tourist, recreational and leisure activities that take place in the marine space and offering hospitality to tourists [11] Luković (2007) Nautical Tourism Defines nautical tourism as the sum of poly-functional activities and relationships that are caused by tourists staying inside or outside the ports of nautical tourism, and by the use of boats or other objects related to nautical and tourist activities, with the purpose of recreation, sports, entertainment or other needs [17] Favro; Kovacic and Grzetic (2008) Nautical Tourism It is characterized as a complex system that requires the use of all the patterns and regularities of the general theory of the system and the principles for the management of integrated complex systems [18] Kovacic and Favro (2012)

Nautical Tourism
Nautical tourism is defined as part of the general tourism phenomenon that has significantly changed the structure and characteristics of the tourism industry [19,20]  It is a type of tourism within general maritime tourism that generates direct impacts on coastal formation and development and that due to its relevance has become one of the most important research areas and has been treated in multiple studies [23] According to these definitions, the authors state that nautical tourism is a variant of tourism where the sea is the most important feature and the presence of marinas is a differentiating that meets the complex and growing demand of nautical tourists [24]. Nautical tourism can appear in many different fields of research. Among those which are recognized in scientific and academic fields are on the one hand, cruise tourism, nautical sports or recreation and the charter of boats or yachts. In recent years, another modality, recreational nautical tourism, has appeared and has been identified as that segment of tourism that travels for the realization of nautical (rowing, kayaking, sailing, jet skiing and sports fishing, etc.) and underwater activities [1].
The absence of an exact definition can be a cause for concern, especially when it includes activities that fall under the framework of national legislation. Luković [25] expresses the need to create a definition that best suits the scientific and practical needs of researchers as well as the economic activities involved in the nautical tourism industry. Taking the definition of tourism given by the Swiss authors Hunziker and Karpf as a starting point, and using the details of nautical tourism practice, he defines it as "the sum of poly-functional activities and relationships caused by tourists-boaters who remain inside or outside the nautical tourism ports and through the use of boats or other objects related to nautical and tourist activities, for the purpose of recreation, sports, entertainment or other needs" [25].
These developments have led to an interesting field of bibliometric analysis, based on two elements: scientific publication as an indicator of the results of said research [26], and the citations received to measure its impact scientist [27].
The present work aims to analyze the scientific production from 1986 to 2019, through its inclusion in impact journals of the Web of Science (WoS) and Scopus databases. This analysis is carried out using the terms, "nautical tourism", "maritime tourism" and "marine tourism". It also identifies, through the analysis of keywords the most used terms and future trends in the research. The main contribution of this research is focused on the integration of marine and nautical tourism in the subsectors that compose the blue economy, since it is a key element in guaranteeing the sustainability of these activities and their alignment with the objectives that establish the blue growth strategy. Another benefit that this research can offer is that it can be considered as a starting point for professionals, experts, researchers, and the general public who are interested in this topic.

Materials and Methods
This article was developed using the methodology of bibliometric analysis which consists of studying the scientific activity of authors and has been used in various areas [28].
Bibliometrics is based on an interpretive profile of researchers by means of a selection of keywords, the choice of databases, title, content of the articles and their abstracts [29].
According to Hall [7], bibliometric research can be applied to the research field of tourism since it can evaluate the quality of tourism research through a ranking of research journals. However, he admits that the use of metrics in tourism studies is complicated due to the scarce availability of appropriate databases which include journals specialized in tourism studies. This research is based on articles published in scientific journals and identified by means of a systematic bibliometric analysis of the literature of the central theme of this study.
The databases chosen for the analysis were Wos and Scopus. The objective of making the comparison is justified because on the one hand Scopus covers more magazines and its citation analysis is faster than WoS [30]. However, WoS citation analysis provides more comprehensible graphics and is more detailed than Scopus citation analysis [31].
These comparative studies of WoS and Scopus concluded that these two databases are always improving. Non-inclusion was estimated for the Google Scholar study due to the lack of quality control in the questions about its suitability as a bibliometric tool [32].
The analysis itself followed a sequence of stages. In the first stage, the search criteria selected included the terms: "nautical tourism", "maritime tourism" and "marine tourism"; the second stage involved the selection of databases, in this case, WoS and Scopus including in the search the terms selected from first stage by article title, abstract and keywords; in the third stage the article filter was applied; in the fourth stage the resulting data from the selection was obtained; In the fifth stage the data was exported using the Vosviewer software program and finally, in the sixth phase, the results were analyzed Figure 1. of keywords, the choice of databases, title, content of the articles and their abstracts [29].
According to Hall [7], bibliometric research can be applied to the research field of tourism since it can evaluate the quality of tourism research through a ranking of research journals. However, he admits that the use of metrics in tourism studies is complicated due to the scarce availability of appropriate databases which include journals specialized in tourism studies.
This research is based on articles published in scientific journals and identified by means of a systematic bibliometric analysis of the literature of the central theme of this study.
The databases chosen for the analysis were Wos and Scopus. The objective of making the comparison is justified because on the one hand Scopus covers more magazines and its citation analysis is faster than WoS [30]. However, WoS citation analysis provides more comprehensible graphics and is more detailed than Scopus citation analysis [31].
These comparative studies of WoS and Scopus concluded that these two databases are always improving. Non-inclusion was estimated for the Google Scholar study due to the lack of quality control in the questions about its suitability as a bibliometric tool [32].
The analysis itself followed a sequence of stages. In the first stage, the search criteria selected included the terms: "nautical tourism", "maritime tourism" and "marine tourism"; the second stage involved the selection of databases, in this case, WoS and Scopus including in the search the terms selected from first stage by article title, abstract and keywords; in the third stage the article filter was applied; in the fourth stage the resulting data from the selection was obtained; In the fifth stage the data was exported using the Vosviewer software program and finally, in the sixth phase, the results were analyzed Figure 1.  The preliminary search of the WoS database, without the application of any filters, retrieved a total of 405 documents. These results were subsequently refined with the search criteria previously defined, selecting only articles contained within the Core Collection of the Web of Science. The result of this filter obtained 242 documents.
In the case of the search in the Scopus database, articles, titles and keywords were selected, obtaining a total of 501 documents. This preliminary result was subsequently filtered to only include scientific articles obtaining a final tally of 333 articles.
Once the results were obtained, they were exported and processed using the Vosviewer program and subsequently analyzed. From these files, it is selected to create a map based on bibliographic data. The type of analysis is co-occurrence relating the items by the number of documents in which they occur together and fractional counting with 2 minimum number of occurrences of a keyword of 1.107 keywords in Wos 224 meet the threshold and 1.823 keywords meet 395 the threshold in Scopus, respectively.
Additionally, the tool Bibliometrix is used, which was developed in the statistical and graphic language R, being quite easy to automate the syntactic analysis and to create new functions and graphics for three metrics at different levels: sources, authors and documents, as well as to analyze the knowledge structures at a conceptual, intellectual and social level [33]. Table 2 displays information about the evolution of the number of articles cited, citations per article (average) and their h-index during the study period. The evolution in the number of published articles shows an increasing trend in both databases. The number of articles was greater for WoS between 2014 and 2017; although this trend was reversed in 2018 with Scopus containing a greater number of articles in that year, this can be due to the number of articles-especially in top-tier journals-that are not yet in any issue and are still on the online version, which does not appear in the WoS search. Between 1986 and 2002 there were scarcely any publications in either database. However, as from 2007, there was a significant growth in publications in both databases, especially in Scopus.    If the scientific production of articles is compared to the period of the financial economic crisis (2008-2014), we can observe there was a rebound in the number of publications on WoS one year before the financial crisis, which had attained its peak in 2014. The most relevant articles on WoS, were, on the one hand, related to tourist ports (marinas) and their planning, the deseasonalization of nautical tourism, and on the other hand, several case studies on the development of nautical tourism in Croatia, the Shiretoko National Park (Japan), Montenegro, Belgrade and Malaysia. The most cited article in 2014 addressed maritime tourism and terrorism and the perception of clients about this threat in the cruise industry [34].

Evolution in the Number of Publications per Year
In the case of Scopus, it reached its peak volume of publication in 2015, where the topic discussed was marine mammal educational tours, marine tourism in light of global climate change, the motivations for recreational fishing in Mallorca and the critical factors of the maritime yachting tourism experience. If the scientific production of articles is compared to the period of the financial economic crisis (2008-2014), we can observe there was a rebound in the number of publications on WoS one year before the financial crisis, which had attained its peak in 2014. The most relevant articles on WoS, were, on the one hand, related to tourist ports (marinas) and their planning, the deseasonalization of nautical tourism, and on the other hand, several case studies on the development of nautical tourism in Croatia, the Shiretoko National Park (Japan), Montenegro, Belgrade and Malaysia. The most cited article in 2014 addressed maritime tourism and terrorism and the perception of clients about this threat in the cruise industry [34].
In the case of Scopus, it reached its peak volume of publication in 2015, where the topic discussed was marine mammal educational tours, marine tourism in light of global climate change, the motivations for recreational fishing in Mallorca and the critical factors of the maritime yachting tourism experience.
When analyzing the period following the economic recovery, that is, 2017 until 2019, these years saw the greatest number of articles published in both databases. On Scopus, the most relevant articles are linked to the issues of safety and risk management in nautical tourism, the quality of web communication, the sustainability of recreational navigation and nautical tourism as a trigger in the development of the Croatian economy. These issues coincide with the articles contained within WoS, although they have also addressed the occupancy tax of nautical tourism in the Mediterranean and the problems and prospects of nautical tourism in Croatia and Portugal. The most cited article was entitled "Trends in ocean and coastal tourism: The end of the last frontier?" (Hall [14]), a review of the literature on coastal and marine tourism focusing on the environmental impacts of the tourism industry as well as the strategies that are used to sustainably manage tourism.
the occupancy tax of nautical tourism in the Mediterranean and the problems and prospects of nautical tourism in Croatia and Portugal. Figure 3 shows the evolution in the number of total citations. WoS reached its peak number of citations in 2001 with 230 citations, a number surpassed by Scopus which obtained 291 citations. In 2015, the highest h-index was obtained in both databases, in WoS with 17 articles, 171 citations and an h-index of 9 and in Scopus with 22 articles, 245 citations and an h-index of 11. The most cited article was entitled "Trends in ocean and coastal tourism: The end of the last frontier?" (Hall [14]), a review of the literature on coastal and marine tourism focusing on the environmental impacts of the tourism industry as well as the strategies that are used to sustainably manage tourism. Table 3 ranks the 10 most cited articles on Scopus ordered from highest to lowest in terms of the number of times it is cited. The articles deal with various topics related to case studies on environmental conservation and benefits of marine tourism, activities such as the benefits and threats of scuba diving, whale watching, the rise of marine tourism, the rights to fishing property and the cruise industry, sustainable tourism planning and the motivations of tourist travelling to marine destinations.   Table 3 ranks the 10 most cited articles on Scopus ordered from highest to lowest in terms of the number of times it is cited. The articles deal with various topics related to case studies on environmental conservation and benefits of marine tourism, activities such as the benefits and threats of scuba diving, whale watching, the rise of marine tourism, the rights to fishing property and the cruise industry, sustainable tourism planning and the motivations of tourist travelling to marine destinations. If the classification is by categories in Scopus, the two most weighty areas of research are social sciences (23.9%), followed by environmental sciences (19.9%), business, management and accounting (14.2%), engineering (10.5%), agriculture and biological sciences (9.2%) and the rest are made up of other areas such as earth and planetary sciences, economics, econometrics and finance and chemical engineering. Table 4 shows the six authors with the highest scientific production in terms of articles on the WoS and Scopus databases based on the selected search criteria. According to the WoS database, the author with the highest number of published articles is Kovačić with 13 articles, 67 citations and an h-index of 5. She is followed by the author Luković who has 9 published articles, 27 citations and an h-index of 3. The authors belong to the University of Rijeka and Dubrovnik University, both located in Croatia. In third position of this ranking, we highlight Saayman for having the highest number of citations and average of the sample (12.83%) from the University of North West in Porchefstroom, South Africa. The remaining authors: Kizielewicz, Gračan, and Favro each have between four and five articles, with few citations and h-index values between 1 and 3.

Analysis of Authors, Research Centers and Countries
With regards to the Scopus database, the ranking is led by Kovačić with 15 articles, 50 citations and an h-index of 4, followed by Luković with 11 published articles, 22 citations and an h-index of 3. The authors. Favro, Gračan and Gržetić have h-indexes between 1 and 3. Once again, the principal distinguished author is Saayman with 9 articles and 120 citations and the highest average of 17.14 and an h-index of 5. These figures are well above those of the other authors. Figure 4 shows the evolution in the scientific production of the most relevant authors over the time, the circles in the cluster map shows the proportion of articles and the color intensity, the greater proportion of citations it has received per year. According to the visualization, the highest rate of publication of articles occurs in 2007, being until 2011 the most prosperous years and the authors with more continuity are Kovačić and Gračan. From 2018 onwards, there is a growth in production with the appearance of new authors Leon and Luck in this field of research. over the time, the circles in the cluster map shows the proportion of articles and the color intensity, the greater proportion of citations it has received per year. According to the visualization, the highest rate of publication of articles occurs in 2007, being until 2011 the most prosperous years and the authors with more continuity are Kovačić and Gračan. From 2018 onwards, there is a growth in production with the appearance of new authors Leon and Luck in this field of research.    The following table (Table 5) shows the scientific production by country according to the Wos database by region and frequency of occurrence.  The following table (Table 5) shows the scientific production by country according to the Wos database by region and frequency of occurrence. The results show that the locations with the greatest concentration of research in nautical tourism are in Croatia, specifically in coastal regions such as Rijeka, Dubrovnik and Split. Croatia leads the rankings both in terms of authors and research centers in this field of research. In fact, the Croatian authorities have positioned nautical tourism as one of the top products of their 2020 tourism development strategy.

Analysis of Journals
An analysis of the most prominent journals publishing articles with the search terms previously defined, reveals that on Scopus, 39.94% of the articles are concentrated in 11 journals based in the United States, Croatia and England with the remaining 60.06% are distributed in a total of 137 journals Table 6. An analysis of the sample reveals the impact factor, the h-index, total cites, and self cites, category, quartile and country of the journals. The results show that the journal with the highest impact factor is Current Issues In Tourism followed by Marine Policy and Marine Pollution Bulletin, ranked second and third, respectively, though the journal with the highest number of citations and h-index is Nase More.  With regards to the WoS database Table 7, of the journals that have the most articles published in the search criteria, five of these are currently being evaluated and are included in the WoS Emerging Sources Citation Index. The journal with the greatest impact factor is Tourism Management, this is followed by Marine Pollution Bulletin and Marine Policy, though the journal with the highest number of published articles, citations and h-index is Ocean and Coastal Management.

Analysis of Relationship
The three fields plot displays 3 fields: the authors on the left side, the keywords in the middle and the resources on the right side. Through this graph it is possible to see the frequency of each element represented by the size and the interrelationship Figure 6. In this instance, the keywords represent the topic of study being the most representative in order of frequency for the nautical tourism, marine tourism and tourism. Regarding authors, Kovačić, Luković and Favro have published the greatest volume of articles in Pormorstvo and Nase More, the scientific journals that are catalogued as emerging sources In this instance, the keywords represent the topic of study being the most representative in order of frequency for the nautical tourism, marine tourism and tourism. Regarding authors, Kovačić, Luković and Favro have published the greatest volume of articles in Pormorstvo and Nase More, the scientific journals that are catalogued as emerging sources in the citation index. It is also important to highlight the authors Saayman and Van der Merwe who, despite having a smaller proportion of articles, are focused on the topic of marine tourism with publications in journals of greater impact such as Marine Policy and Ocean Coastal Management.

Trend Analysis
Through an analysis of the keywords of these articles, the most commonly used terms have been identified and the most current trends related to emerging areas of interest in tourism, whether it be nautical, marine or maritime tourism are also revealed. The trend graphs obtained using Vosviewer use a color scale that ranges from blue to red and categorizes the terms used in this field of study from the least to the most innovative in the period studied.
In Figure 7, and in relation to WoS, shows the trends linked to concepts such as website quality, the blue economy, the impact of tourist ports, marine resources, marine protected areas, knowledge, stakeholders, models and sensitivity. According to Scopus Figure 8, the trends focus on concepts related to the blue economy, tourist ports, bio-ecoregions, website quality, residents, coastal marine tourism and maritime spatial planning (MSP). As for the MSP, its competence has been considered a priority issue, since there is a need to manage water to ensure that activities in this environment are carried out in a safe, efficient and sustainable manner. Because of its potential and relevance to the implementation of ocean management and operational governance, the MSP has gained considerable importance over the last decade, and many nations around the world have begun to develop their own spatial planning processes [44,45]. An example of the concern for maritime spatial planning is to be found in the European Union in Directive 2014/89/EU of the European Parliament and of the Council of 23 July 2014 establishing a framework for maritime spatial planning promotes sustainable use and appropriate allocation of maritime space, recognizing that marine waters, ecosystems and resources are under significant pressure from human activities, the effects of climate change, natural disasters and coastal dynamics which can impact on coastal development and economic growth. According to Scopus Figure 8, the trends focus on concepts related to the blue economy, tourist ports, bio-ecoregions, website quality, residents, coastal marine tourism and maritime spatial planning (MSP). As for the MSP, its competence has been considered a priority issue, since there is a need to manage water to ensure that activities in this environment are carried out in a safe, efficient and sustainable manner. Because of its potential and relevance to the implementation of ocean management and operational governance, the MSP has gained considerable importance over the last decade, and many nations around the world have begun to develop their own spatial planning processes [44,45]. An example of the concern for maritime spatial planning is to be found in the European Union in Directive 2014/89/EU of the European Parliament and of the Council of 23 July 2014 establishing a framework for maritime spatial planning promotes sustainable use and appropriate allocation of maritime space, recognizing that marine waters, ecosystems and resources are under significant pressure from human activities, the effects of climate change, natural disasters and coastal dynamics which can impact on coastal development and economic growth. If we categorize the trends of the keywords in both databases, three main groups appear: "blue economy", "website quality" and "tourist ports". The blue economy is considered a recent field of study and covers the economic activities that depend on the integration of the sea with other sectors: tourism, marine transport and fishing among others. In addition, there is an interdependent relationship between these activities as they share port infrastructures, logistics and energy. In turn, the tourist ports and marinas are companies that offer services to the shipping and boating sectors, and part of their marketing and communication strategies include the use of websites. In this regard, a recent study revealed that the tourist ports in the Mediterranean area do not fully exploit the potential of websites, as not all the information contained within them is up to date or in many cases they do not provide all the expected information and often lack effective search capabilities or a menu and only a few have a mobile version [46]. It is therefore interesting to take advantage of the development of internet technologies and the maturing of mobile commerce to contribute to the intelligent development of marine tourism [47,48].

Discussion
In the extant literature there is no consensus or clarity regarding the differences between nautical, maritime and marine tourism [49]. In general terms, the most global and decisive element attributed to nautical tourism is the link to sports activities at sea [13] or that can be carried out in rivers and lakes [50]. As previously discussed, there is no exact definition of the concept of nautical tourism because, as various authors point out, of its complex connections with maritime, shipping or boating activities [25]. Other definitions of nautical tourism start from the perspective of the tourism product itself and link it to the practice of leisure activities in direct contact with the sea [51]. There is a dilemma with certain activities such as surfing, which can be considered a type of marine or nautical tourism [52] when the objective is leisure, and in other documents it is considered an independent sector and even a type of sports tourism more focused on competition and training [53]. Other authors claim that surfing is a sporting activity that has become an important business, integrated into the leisure and tourism industries [54,55].
Nautical and maritime tourism is considered a subsector of the tourism sector and the so-called blue economy. However, according to official statistical data, there are no separate features that relate it to the broader sea or maritime sector as this is understood to be a set of economic activities that are related to the sea. This broader sector is currently defined by the classic understanding of whether or not the economic activity uses natural If we categorize the trends of the keywords in both databases, three main groups appear: "blue economy", "website quality" and "tourist ports". The blue economy is considered a recent field of study and covers the economic activities that depend on the integration of the sea with other sectors: tourism, marine transport and fishing among others. In addition, there is an interdependent relationship between these activities as they share port infrastructures, logistics and energy. In turn, the tourist ports and marinas are companies that offer services to the shipping and boating sectors, and part of their marketing and communication strategies include the use of websites. In this regard, a recent study revealed that the tourist ports in the Mediterranean area do not fully exploit the potential of websites, as not all the information contained within them is up to date or in many cases they do not provide all the expected information and often lack effective search capabilities or a menu and only a few have a mobile version [46]. It is therefore interesting to take advantage of the development of internet technologies and the maturing of mobile commerce to contribute to the intelligent development of marine tourism [47,48].

Discussion
In the extant literature there is no consensus or clarity regarding the differences between nautical, maritime and marine tourism [49]. In general terms, the most global and decisive element attributed to nautical tourism is the link to sports activities at sea [13] or that can be carried out in rivers and lakes [50]. As previously discussed, there is no exact definition of the concept of nautical tourism because, as various authors point out, of its complex connections with maritime, shipping or boating activities [25]. Other definitions of nautical tourism start from the perspective of the tourism product itself and link it to the practice of leisure activities in direct contact with the sea [51]. There is a dilemma with certain activities such as surfing, which can be considered a type of marine or nautical tourism [52] when the objective is leisure, and in other documents it is considered an independent sector and even a type of sports tourism more focused on competition and training [53]. Other authors claim that surfing is a sporting activity that has become an important business, integrated into the leisure and tourism industries [54,55].
Nautical and maritime tourism is considered a subsector of the tourism sector and the so-called blue economy. However, according to official statistical data, there are no separate features that relate it to the broader sea or maritime sector as this is understood to be a set of economic activities that are related to the sea. This broader sector is currently defined by the classic understanding of whether or not the economic activity uses natural resources, whether the activity involves processing or transforming these resources or if they are related to the services sector. According to an article by González and Collado [56], the broader maritime sector is defined as "a group of companies whose activity is directly related to the maritime", comprised of fishing companies, transport, repair and naval maintenance, auxiliary and port services, and those companies related to recreational water sports and nautical activities. Ferradas [57] affirms that there is still much to be done for nautical tourism to reach its full potential through the analysis of the demand and selecting the appropriate market for promoting nautical tourism. In the article on "Emerging ocean industries: implications for the development of sustainable tourism" [58], Dwyer addresses the present and future economic value of the world's oceanic industries and the contribution of the tourism industry in particular, as well as their impact on coastal and marine tourism as a consequence of its own growth.
The blue economy presents great opportunities for economic development [59], such as in large ecosystems in Africa where it has generated income, employment opportunities, poverty reduction and climate change mitigation in partnership with sustainable development goals (SDGs).
Participation in sports, in this maritime environment, has become increasingly popular [60,61] and nautical tourism has positioned itself as one of the most developed segments of the last twenty years within the tourism and leisure market worldwide [20,62,63]. It has also been claimed that nautical tourism is one of the most stable and dynamic forms of tourism attracting business activities and foreign investments, in addition to a greater involvement of the pertinent public administrations in order to encourage the further development of the nautical tourism sector attracting tourists. These nautical tourists have a high level of purchasing power that, on the one hand, activates the economy of the area, the supply of tourism products, thus creating greater growth of the sector [64,65] and, on the other hand, promotes greater interest in investing in the construction of marinas and nautical tourism due at its high rates of return [66].
Aside from the economic benefits, the development of the coastal tourist destinations plays a fundamental role in the seasonality of tourism activity [67] and complements the more traditional "sun and beach" tourism. The activities developed around sailing have generally been considered to be an elitist product or as just another sport. In this regard, Ferradas [13] proposed a solution by promoting nautical tourism to users and as a leisure product that is part of the tourist activity.
On the other hand, in the institutional sphere, the European Union applied a blue growth strategy in 2012 and established a series of subsectors in the area of the blue economy [68], including "Coastal and Maritime Tourism", which is particularly relevant in the evolution of sea-related tourism to ensure its sustainability [69,70]. Taking into account the evolution of maritime tourism as activities carried out at sea (navigation or deep sea), through a review of the literature and based on the contribution of the authors to this field of research, a new concept is proposed that integrates the subsector of the blue economy and the blue growth strategy, under the name of "blue tourism", with the sea as the protagonist and all those tourist activities of leisure and recreation developed in this environment.

Conclusions
Through bibliometric analysis it is possible to quantitatively analyze the scientific literature in order to analyze the research activity of a given topic. For this specific case, similar results are observed comparing both databases (WoS and Scopus) and the countries that have developed more scientific production in this type of tourism are exactly those where their economic activity is related to the sea, the coast and nautical and maritime activities. Despite the scarcity of investigations in the academic field that is the central theme of this study, 2007 was a turning point in both the WoS and Scopus databases with a greater number of articles being published in scientific journals, as well as the increase in the number of citations.
Finding a definition of the concept of nautical tourism remains a complex issue as there are many component factors and elements. It is a definition that is evolving as the activities that arise and are incorporated into nautical, maritime, marine and the tourism sector in general are constantly changing. For this reason, the term "blue tourism" is proposed as a conceptual solution that encompasses maritime, nautical and marine tourism. Blue tourism means holiday activities or events that involve traveling for pleasure combined with boating and maritime activities in a sea environment in a sustainable way. For the coastal areas that have marinas, its implementation is an element that makes a difference and adds value compared to other locations, improving the tourist offering and having a decisive role in the economy due to the importance of a good territorial, safety and sustainable environmental planning.
As regards the dilemma that arises when classifying certain nautical activities, it is important to identify the objective of carrying out this practice, i.e., an activity can be considered as sports tourism when the objective is training or competition or it can be nautical tourism when the objective is sailing, recreation and leisure or simply be a means of transport when there is no direct relationship between the tourist and the means of transport.
The main thematic areas of research are focused on social sciences, environmental sciences, engineering and business, management and accounting. According to the trend analysis, future lines of research include a focus on the blue economy, the quality of websites and the emergence of tourist ports. An interesting line emerges in order to fulfil the objectives of sustainable development (SDGs) and how nautical, maritime and marine tourism can contribute to the protection and sustainability of the ecosystems without slowing down the economic, social and cultural development of the populations.
The maritime transport sector and the ports allow many countries to take advantage of the rapid growth of international trade and to exercise leadership in the world economy, with activities arising from nautical-sports activity, tourism and the ecosystem services it offers being relevant. Therefore, guaranteeing the conservation of the marine environment constitutes one of the central axes for industries that depend on this environment to be competitive, responsible and sustainable (economic, social and environmental). The sustainability of the oceans is a major global challenge that is closely linked to climate change.
One of the limitations of this research is the complexity of finding an agreed definition of the main terms of this research. It is therefore interesting to channel future research into the contributions that this sector can make to the blue economy.
Undoubtedly, maritime resources generate numerous benefits to the coastal economy and offer important opportunities for leisure, local development in coastal areas, tourism, recreation and scientific research possibilities.