Shark Attack 3: Megalodon
(2003)

Ben (John Barrowman) drives the submarine into the Megladon when the homing beacon fails, hoping that the torepdo will target the submarine instead.  He swims to safety as the torpedo detonates.  Ben, Cataline, and Chuck all survive, though none of the the higher-ups at Apex who allowed this to happen do.  Everyone rejoices, failing to notice the second Megladon swimming just below the surface.

Thanks Mary C!