In Brazil, Gloria's father is bankrupt, so he asks her to take the son of his potential financial savior on a day of boating planned with her boyfriend Danny and their best friend Jeff. Marcos our son in question, is wealthy, good-looking, muscular but, because of a childhood illness, a seriously bad swimmer. Gloria is a materialist and a flirt, who's happy to tease Danny with Jeff as she is with Marcos. Showing up at an island to explore and dive in it's lagoon. Gloria secretly keeps leading Marcos on. When Danny sees them locking lips, she cries sexual assualt and her livid boyfriend throws a protesting Marcos overboard...with only a lifering for company. Danny decides to let Marcos sweat it out for a while by then driving the boat to the far side of an island...but engine trouble prevents them from returning too soon. So when they return, Marcos is now missing in the strong currents, presumed drowned. Panic sets in and soon after so does murderous self-interest.