Tess Finnegan (Kate Hudson) and her ex-husband Ben (Matthew McConaughey), who met and married in Florida during spring break, have spent their entire marriage looking for the booty. Tess is a doctoral candidate and has had her whole life thwarted by Ben's passion for finding the Dowry. So they split up, but immediately get back together when Ben finally finds a substantial clue to what's down there, waiting.
Meanwhile, Ben's underwater wanderings have put him in serious debt to a gangster/rap star named Bigg Bunny (Kevin Hart), who wants the treasure, too. And in a stupidly reckless effort to save a windblown hat, Ben endears himself to the dumb-as-a-doorknob Gemma Honeycutt, whose father, the fabulously wealthy Nigel Honeycutt (Donald Sutherland), takes a liking to both Ben and the idea of finding the Dowry.
That Tess is working as a steward aboard Nigel's yacht is one of the picture's many wild coincidences. At this point, she and Ben lay out for Nigel the whole history of the ill-fated ship Aurelia.
Much of the rest of the film consists of musical montages, chase scenes and slapstick comedy.