This is fairly hard- I can come up with many different sailing songs, but songs including fish are more difficult.

I am not going to include U-Tube videos, but here are my additions:

Into the Ocean - Blue October
Hotel Song - Regina Spektor (I dream of orca whales...)
Downeaster "Alexa" - Billy Joel
Car Wash (Shark Tail Mix) - Christina Aguilera

and of course-
Barracuda - Heart