The story for Piranha II doesn't connect to Piranha save for a reference to fish used as bioweapons for a top-secret U.S. Army experiment.  Those experiments continued into cross-breeding piranhas with grunions and flying fish to make them dangerous in both air and water. A ship has sunk and a container of their eggs breaks open in the area near Club Elysium, a posh Jamaican resort, on the verge of their annual Fish Fry Beach Festival, when the grunions hatch and walk upon the shore.

That's where Anne (Tricia O'Neil), a marine biologist, works as a scuba instructor. Anne's separated husband Steve (Lance Henriksen) is a cop in the seaside town. Steve's a little jealous when Anne enters into a fling with a mysterious resort resident, Tyler Sherman (Steve Marachuk). When human bodies are found in a gruesome, half-eaten state, they suspect other summer frolickers are in danger.  Too bad Club Elysium won't shut down the highly attended festival.

James Cameron's directorial debut.