Could it be a lunger? Ewwww that can't be it. I'm gonna have to say Tarpon. Reason is I saw a show where they were catching them and the guy said that sometimes they gulp air during a fight when on top of the water and that revitalizes them. Just my semi-edjumicated guess.
Tommy Wins !
A Tarpon is a species that has remained virtually unchanged since it's prehistoric ancestors. Tarpon have a "semi developed" lung wich is the reason why they so often roll through a channel while swimming along. I have seen many tarpon rolling, especially at night.
Tarpon also have completly funtioning gills. A fish that has evolved perfectly to suit it's environment.