A sea monster movie with some actually pretty excellent underwater cinematography, presumably paid for by all the money they saved on shirts.

Twenty years ago, a family enjoys an idyllic vacation on their small sailboat, until a giant squid attacks the boat, kills both adults, and leaves the kid a traumatized orphan. Fast forward twenty years and a brilliant, bikini-topped archaeologist leads an expedition to find an ancient Greek opal. According to legend, the opal was guarded by the sea monster Scilla before being stolen by the Greeks, stolen again by the Romans, and traded across Eurasia throughout history. She's out to prove her crackpot theory that it was sunk on a Chinese freighter in the Pacific Northwest by searching the Pacific Northwest for a sunken Chinese freighter containing the opal. Finding it would prove she's not a crackpot after all, and allow her to get tenure without ever having to put on a shirt. And now her assistants, Shirtless Hunk Grad Student and Bikini Grad Student, have spotted a probable sunken Chinese freighter. Unfortunately, as their boat's Captain is retrieving their camera-equipped minisub, he's attacked by a kraken and tangled in the ship's net. He screams for help and Shirtless Hunk Grad Student, who has the brains of a pork chop, runs to the bridge and guns the throttles, turning the net into a cheese grater. Fortunately, nobody notices either the kraken or Shirtless Hunk Grad Student's incompetence and the whole thing is written off as a tragic accident.

Unfortunately, the ship's engine is damaged and they're also down a Captain. Luckily, no sooner do they arrive back at the dock when Hero, the traumatized kid all grown up, shows up and he's conveniently both a mechanic and a licensed captain. Archaeologist is skeptical at first, but quickly won over by his ability to fix the engine and willingness to take off his shirt. She even agrees to go on a date with him. Before that happens, though, a Greek Mobster and his henchmen shows up. He's the black sheep of his crime family, hence his exile to the Pacific Northwest, but if only he can get the opal (which rightfully belongs to his family) he can buy his way back into their good graces. Also, he and all his goons are wearing shirts, just in case there was any question they were evil.

After some banter, the Archeologist goes back to her hotel room to clean some artifacts in her underwear. Hero shows up and, since this is now a romantic personal event rather than a professional work one, Archaeologist puts on a shirt (well, a tank-top; let's not get carried away here!). The date progresses and there's some intimation that the dress code is about to get more professional when things are interrupted by the Greeks firebombing the boat, which kind of kills the mood. It gets even worse the next morning when the University refuses to buy another boat and orders the Archaeologist to come back to campus and put on a damn shirt.

Just as all seems lost, Hero shows up at the docks, having sunk his life savings into buying a new boat to continue the expedition. This seems like a serious red flag that he's either reading waaaay too much into one date or he has an Ahab-level squid stalking problem. But with little alternative, the Archaeologist agrees that the expedition is back on. Unfortunately, by the time they get back to the wreck, the Greeks are already there. There follows a great deal of shirts vs. skins pirate hijinks during which Shirtless Hunk Grad Student takes a bullet for Bikini Grad Student; Bikini Grad Student is, in turn, eaten by a kraken; Greek Mobster throws a bunch of his henchmen to the kraken for no real reason just in case the shirt wasn't sufficient evidence of his evil; and lots of boats blow up. In the end, though, the girl gets the opal and lives happily ever after.

What? No, not the Archaeologist. The kraken! Who did you think was the hero of this movie?