Made in 1981, this is a routine monster film, unrelated to Joe Dante’s 1978 Piranha. Idiotic premise has US government genetic engineering experiments creating a deadly form of grunions (hinted at being used in the Vietnam war). A missing canister of fertile eggs of these mutant fish (called piranha for horror fans’ sake) turns up in the Caribbean resort of Club Elysium and the beasties start chewing up vacationers.
Film’s title refers to the grunions’ annual mating ritual of spawning on the beach. Lame script pokes fun at the match of human and fishy mating rites. Nominal human interest plot has Club Elysium scuba diver Anne (Tricia O’Neil) teaming up with incognito biochemist Tyler (Steve Marachuk) to discover and blow up the fish, while her estranged husband Steve (Lance Henriksen) looks out for the welfare of the locals as the film’s Roy Scheider-esque cop.
Exec producer Ovidio G. Assonitis follows up his similar made-in-America horror pics Beyond the Door, Tentacles, and The Visitor with an Italian-crewed film which easily passes as All-American. Special effects experts come up with convincing gore for the victims, but the monsters are laughably phoney.