The Hawaiian Archipelago is home to many small islands, and amongst them is the beautiful and isolated Mahu Island. A popular destination for vacationers, Mahu is home to the usual assortment of creeps and charlatans that like to lurk around tourist traps and take advantage of the naive folks from out of town. Greg Oliver (Sam Bottoms) and his mangy uncle Earl Sullivan (Virgil Frye) are two such people. They run a boat tour business that actually specializes in conning tourists by taking them on phony underwater treasure hunts. Greg and Earl's antics continuously antagonize Oscar Forbes (Kedric Wolfe), manager of the nearby Tropical Palace Hotel, where Greg's girlfriend Rachel (Susanne Reed) works.
This tourist season, though, it's not just business as usual for anybody. The trouble starts when local marine biologist Dr. Whiting (Charles Howerton) sends his young female assistant scuba diving into the deep for specimens, only to be horrified when a cloud of bloody water floats to the surface and she is never seen again - though her severed arm is later found in shallow water by a local. Then soon after Rachel, who is an aspiring model, goes out on a photo shoot to a remote beach with a photographer. Seeking the best possible angle, the unfortunate man wades out into the surf where he is promptly devoured by an unseen sea beast. And the body count only gets higher from there.
Dr. Whiting believes that the disappearances of his assistant and the others are the work of an unknown type of sea creature and is determined to capture it alive. Fishermen have brought him specimens of fish that are of species completely unknown to science, and he hypothesizes that a change in deep sea currents is bringing unknown marine life out of the ocean depths and into shallow coastal waters. But fearing talk of a sea monster will scare all his guests away, Forbes makes a concerted effort to cover up the presence of the monster...at least until Earl talks him into sponsoring a hunt for the creature!
Directed by Cirio H. Santiago / Written by Charles B. Griffith / Color / 85 minutes / iPod-ready MP4 file / Includes bonus short film, "The Basement".