Six billion dollars' worth of treasure is buried in the Caribbean Sea and it's up to the preternaturally attractive Paul Walker, Jessica Alba, and their pals to claim it before the bad guys (Josh Brolin, a mohawked Tyson Beckford) do. While the shark shots, filmed in open water off the Bahamas, will no doubt impress, Alba's close-ups should get more heart rates going. ''She has her own body issues and had very specific ideas of what looked good on her,'' says director John Stockwell (Blue Crush), adding that his star ''auditioned'' hundreds of bikinis for their, uh, supporting roles. ''Only thing was she liked this crocheted bikini that tended to slip and fall and come off in inappropriate situations.'' Before you ask, mouth breathers, her ''bloopers'' will not be on the DVD.