In 1712, a Spanish galleon en route from Barcelona to the New World loaded diamonds and gold sinks (yeah, don't think about that too much) in a hurricane in San Fransisco Bay (again, don't think about that too much). A few hundred years later, a tour guide leads his (teenage? college age?) son Jimmy and a bunch of obnoxious tourists on a scuba diving tour of the wreck, which they inexplicably reach by jumping out of a helicopter rather than taking a boat like normal people. During the tour, they are even more inexplicably attacked by sharks and everybody but the son is killed.
We need to pause here to explain what "attacked by sharks" means in the context of this movie. All shark attacks take the following form: Shots of the actors who are about to die. Stock footage of a shark. More shots of the actors. More stock footage of sharks. A fake shark mouth thrashing about with an unidentifiable wetsuit-clad limb (regardless of whether or not the person being killed is actually wearing a wetsuit) while fake blood is poured into the water, overlaid with screaming. Shots of the surviving cast, which the audience must search to figure out who's missing so they can work out who just died. This is, in short, as dull and mediocre a shark movie as has ever been made.
Anyway, ten years after that, Jimmy is chief beach safety officer in a small California town, despite his extreme phobia of sharks. This year, a mysterious Russian is underwriting the Beach Fiesta and, with the influx of cash, the Mayor will let nothing stand in the way of a successful festival, not even a shark randomly attacking the beach for no reason and killing a dozen swimmers. Assigned to stop the sharks however he can, Jimmy recruits a bunch of his beach bum friends to go shark hunting with him. This involves scuba diving in shark cages to shoot the sharks with tracker darts. Unfortunately, when the stock footage sharks arrive, the divers in the shark cages appear to be unarmed and defenseless when the sharks start bashing against the cages. Rather than letting themselves be trapped in the shark-proof cages, the divers all flee and get eaten while trying to swim back to the boat. Meanwhile, the fiesta goes on and is a huge hit despite all the deaths, including some more random people who take off their shirts and jump in the water to get eaten by sharks (see comment above about wetsuit-clad limbs, despite them being clad only in bikini bottoms). Despite it all, Jimmy eventually figures out where the sharks are lairing, flies over them in a helicopter, and drops explosives on them, saving the fiesta.
Meanwhile, in a totally different movie, the Russian wants the diamonds on the wreck of the galleon. Unfortunately, despite it being about a hundred feet off shore in San Francisco Bay and Jimmy's dad having hovered over it repeatedly in a helicopter, only Jimmy knows where it is. But Jimmy, with his phobia of sharks, refuses to lead an expedition back to the wreck where his father died. The Russian tries political pressure via the Mayor, bribes, and then threats, so Jimmy gives him the location and tells him to go on his own. Hahaha, of course not. Jimmy refuses to disclose the location of the wreck, so the Russian concocts an elaborate plan to hijack Jimmy's son's school bus, kidnap the boy, and use him to force Jimmy to lead an expedition to the wreck. He does and the Russian and his goons are all killed by sharks. The End. No, seriously, I'm not making that part up.
