A Novel Degree of Freedom in Flapping Wings Shows Promise for a Dual   Aerial/Aquatic Vehicle Propulsor
  Ocean sampling for highly temporal phenomena, such as harmful algal blooms, necessitates a vehicle capable of fast aerial travel interspersed with an aquatic means of acquiring in-situ measurements. Vehicle platforms with this capability have yet to be widely adopted by the oceanographic community. Several animal examples successfully make this aerial/aquatic transition using a flapping foil actuator, offering an existence proof for a viable vehicle design. We discuss a preliminary realization of a flapping wing actuation system for use in both air and water. The wing employs an active in-line motion degree of freedom to generate the large force envelope necessary for propulsion in both fluid media. 
Jacob S. Izraelevitz, Michael S. Triantafyllou
physics.flu-dyn