Two teens separately swim towards an abandoned ship, hoping to become pirates. A shark frightens them, but it has a harpoon in its fin, which they remove. On the ship they battle a hurricane, ward off pirates and the Spanish Armada using various clever strategies. While struggling to express their feelings for each other, they discover that they’re already engaged - a marriage their parents arranged without their meeting. A cannonball sinks their ship, but the shark they previously saved delivers them safely to shore. Following a map to buried treasure, they decide to continue their pirate lives together.