I was calling this a "salp" until a friend of mine who is a Marine Biologist sent me the following info: The creature called a "salp" is even weirder than that. Notice that it seems to extrude from a tube. It is in fact a pelagic mollusk called a needle pteropod: Creseis acicula. One finds the shells on the sea floor, usually smashed, but to see the entire creature is rare. It ranges throughout tropical and subtropical seas worldwide.