While vacationing on the Spanish island of Majorca, New York fashion model Anne Traymore meets Manuel del Rio Montoya when he returns the bracelet she lost while swimming in the sea. When Manuel, who works as a caretaker aboard the sleek sailing boat, the Swan , which is owned by Rene Le Clerc, a wealthy Parisian importer, invites Anne to accompany him spear fishing, Anne, thinking that he owns the craft, accepts. As Anne and Manuel explore the sea below, Joe Balfour and Ernie Williams, two shady adventurers in need of a boat, board the deserted Swan with the intention of stealing it. When Manuel and Anne return from their dive, they find Joe and Ernie aboard, and when Joe asks to charter the boat, Manuel arranges to meet him for drinks later to discuss the details. At a nightclub that evening, Joe, who has discovered that Manuel is merely the Swan 's caretaker, enlists Anne's help in convincing Manuel to cooperate. The next morning, Joe shows Anne some Spanish doubloons and then tells her that he and Ernie need the Swan to help them retrieve $3,000,000 in sunken gold. Joe explains that he and Ernie were hauling the gold for its owners when a storm struck, sinking the boat with its treasure and killing all aboard except him and Ernie. When Joe offers Anne a fourth of the treasure in exchange for persuading Manuel to join their venture, she eagerly accepts. After Manuel agrees to let them use the boat, he phones Le Clerc in Paris to advise him that his impending cruise must be postponed because the Swan needs to spend three weeks in dry dock. The next day, the four set sail and Joe assumes the post of captain. As the days wear on, Anne begins to distrust the boorish Ernie. When a threatening storm approaches, Manuel insists on turning back, but Joe blackmails him into continuing by threatening to tell Anne that he is only a poor sailor. In Paris, meanwhile, Le Clerc discovers that Manuel has disappeared with the Swan and flies to Majorca to investigate. When the hurricane hits, the boat and its occupants thrash helplessly in the high seas until the storm subsides. The propeller has been jammed by seaweed and when Joe dives in to free it, he is stung by a portuguese man-of-war. To save Joe's life, Manuel sails the boat to a nearby island and there harvests some medicinal herbs that will counteract the poison. Under Anne's diligent care, Joe gradually recovers. One night on the beach, Manuel fervently proclaims his love to Anne, and after she rebuffs him, he angrily dives into the sea and swims out to the Swan , intending to leave the others stranded on the island. Ernie follows, and as the two battle on board, the Swan drifts precariously close to a rock embankment. Arriving just in time, Joe takes the wheel and steers the craft to safety. Upon reaching the buried treasure, Anne warns Joe to watch Ernie. After days of retrieving baskets of gold from the scuttled ship, the sunken vessel's hull begins to shift dangerously. Consequently, when a shark appears from the deep, Joe declares they have reclaimed enough treasure and it is now time to move on. At Ernie's insistence, however, Joe agrees to extend the hunt for one more day. The next morning, as Joe and Manuel dive for doubloons, Ernie commandeers the Swan , intending to hijack it with Anne and the gold onboard. When Joe tries to stop him, Ernie threatens him with a speargun, but Manuel gets the drop on Ernie and wounds him in the back. Soon after, Le Clerc, who has been tracking his boat, arrives in a small craft and threatens to send them all to prison. He relents, however, when Joe offers to split the treasure with him. They then sail for home, but as they approach the harbor at Majorca, the Coast Guard stops them and confiscates all the gold. Deciding to remain partners anyway, Anne and Joe kiss.