Steven (Hugo Stiglitz), a US-born Mexican businessman arrives in a Mexican fishing/resort village for a much-needed vacation on a yacht anchored off shore. One of the local fishermen, Colonado (Eleazar Garcia), takes Steven with him when he goes to haul in the sharks he has caught. Colonado is annoyed to learn that another shark has taken a huge bite out of one of his captured sharks. Steven says he feels bad for the sharks, then shrugs, "that's life." Steven then decides to scope to local beaches for sexy women. He sets his sights on Patricia (Fiona Lewis), an Englishwoman on vacation. They have a whirlwind romance but break up when Steven can't decide if he is in love with her. Steven is extremely jealous, however, when she begins a relationship with Miguel (Andres Garcia) a womanizing swimming instructor at the nearby resort hotel. While Steven stews on the yacht, Patricia and Miguel have sex in her bungalow. The next morning, she goes skinny dipping in the ocean and is eaten alive by a large, apparently emphysemic tiger shark.The next day, Steven confronts Miguel in the hotel bar. Miguel tells Steven that Patricia was in love with Steven but must have returned to England (however they never find out about her true fate). He introduces Steven to two sisters, Kelly and Cynthia Madison (Jennifer Ashley and Laura Lyons) who are American college students vacationing at the island resort for some loose fun. They have a double date and, on the sisters' suggestions, skinny dip out to the yacht. The shark's heavy, labored breathing can clearly by heard but they make it to the boat safely. Kelly and Cynthia hop back and forth between Miguel's and Steven's beds. They all swim back to shore the next morning and the shark again chooses not to bother them.Miguel encourages Steven to live a carefree, womanizing life like he does. Steven agrees. They even start a shark hunting business, swimming out to sea and shooting whatever swims past them from local blue sharks to lemon sharks. Miguel tells Steven that if a tiger shark ever appears, they must immediately get out of the water because tiger sharks are too dangerous to even attempt to hunt.One night, Miguel and Steven meet Gabriella (Susan George), another Englishwoman on vacation at the hotel bar. The three of them decide to have a triad: Gabriella will be sexually involved with both of them but they won't fall in love with her, or she with them. They tour the local Mayan archaeological sites together, then retire back to the yacht for sex. Miguel and Steven take Gabriella shark hunting with them. She is appalled by what they do, but admits her feelings for them have become powerful and as such apparently forgets her distaste. The next time the three go shark hunting, the emphysemic seven-foot tiger shark appears and rips Miguel in half. Steven is bummed out but Gabriella is so upset that she decides to leave Mexico.Steven vows revenge on the shark. He enlists the local coast guard and fishermen in a campaign to kill the tiger shark and apparently every other shark in the sea. Colonado is disturbed that Steven viciously beats the sharks with a club. "I hate the bastards," Steven tells him. Colonado assures him that so many sharks have been killed, the tiger shark must have been one of them. Meanwhile, unbeknown to Steven or Colonado, the tiger shark attacks another small fishing boat and eats two fishermen.Steven goes to a nighttime beach party with Kelly, Cynthia and two other women he met in a bar (Priscilla Barnes and Pamela Garner) whom are in the company of Criquet, a local pimp and businessman. After the party ends, Kelly and Cynthia suggest everyone skinny dip again. This time, however, the tiger shark attacks, ripping Cynthia from Steven's arms as he tries to make out with her in the water. It also injures the other two women, both of whom safely make it ashore. Steven contacts Mr. Madison (Carlos East) who comes to the village to collect Kelly from the hospital. Steven vows to kill the shark himself. That evening, Steven lures the shark with a devilfish he has speared for the occasion, and when he hears the shark's rasping approach shoots it with a speargun which has an armed stick of underwater dynamite on the tip. However, the shark takes his arm off in the process, but is finally destroyed in an explosion of blood and guts.Steven awakens in a hospital room, sans his right arm, thinking happy thoughts about his triad with Gabriella and Miguel.