Watch full movie online. Underwater Upside Down is an oddball comedy about two Malibu brothers whose parents tragic death 20 years ago left them with a whole lot of money, a ton of ambition and a toolbox devoid of tools. With a squandered inheritance and one week to salvage their future, they have to navigate their way through a world of Russian contractors, tween actresses, aging hippies and golf-club billionaires. Last thing they want is a naked amnesiac showing up at their door... But maybe she's exactly what they need.