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[General SciFi] Aquatic aliens

So I have been thinking and it seems reasonable to say that an aquatic or semi-aquatic species would have an easier time traveling in space and such because they can just pressurize water in their ships. Also they're used to not really having an up.
What do you guys think?
gpt
Aquatic species have a massive number of hurdles to overcome before they can even try to build a spaceship.

Living underwater means no fire, this means...

- No ability to keep yourself warm in cold environments, this means that their expansion on their own planet would be limited to warm environments. This would limit population growth and access to raw materials. 

- Being unable to cook food limits your potential food sources. We rely on a massive number of foods that are toxic or inedible in their uncooked state (e.g. potatoes). Cooking breaks down complex chemicals into a more digestible form. The ability to cook food allows greater expansion into areas where your traditional food sources are not available. Not being able to cook food restricts the food supply, in turn limiting population growth, and geographic growth into areas where raw edible food cannot be grown, again limiting access to raw materials.

If the human race did not have fire, most of Europe, Canada, the Northern States of America, Russia, Siberia, Alaska and Northern China would all be uninhabitable and our diet would be restricted to fruits, fresh meat, lettuce and whatever other vegetables you can eat raw. Without foods like potatoes or corn, agriculture, and in turn, our population density would be limited, preventing the formation of large cities, required to form the kind of society that creates scientific knowledge.

No fire also means...

- No ability to smelt metal. Some metals like Gold can be found in their raw form, but most require smelting from ore. The inability to smelt means no Bronze Age, no Iron Age. The best tools they'd be able to make would be stone, they'd literally be stuck in the Stone Age forever.

Should they somehow get past that, living underwater poses a number of other problems when trying to develop "science".

- Most early chemistry was learned by mixing liquids together, or placing a solid in a liquid and measuring the results. That's simply impossible to do underwater. Trying to perform a chemical reaction when the entire environment is a solvent will produce no worthwhile results.

- Trying to learn about electricity while underwater would be equally pointless. Before you can start building batteries and transistors, you need to understand what electric charge is, what a conductor is, what an insulator is. Water conducts electricity, any charge that is built up will be instantly dissipated, making it near impossible to study. Even if you could somehow build a battery underwater (see above about trying to make sulfuric acid and lead plates) the charge would be conducted by the environment, causing it go flat incredibly quickly. No electricity means no electronics, no computers..

Should they somehow overcome all these problems and develop a society on a par with 20th Century humans, a spaceship full of water weighs massively more than a spaceship mostly filled with air. The Apollo Lunar Ascent module weighed 4,500 kg. Filling it with water would add another 7000 kg to that (plus additional fuel to carry the extra weight, additional weight for reinforced structure). 

Manned spaceflight, even just orbital flights, would be unattainable for them using rocket technology.

TL:DR An aquatic species would have a hard time ever making it past the stone age.