More than 17 years ago, when he was still an infant, Spencer Elden's parents dropped him into a swimming pool in California, where underwater photographer Kirk Weddle was waiting to snap an entire roll of film of the naked, buoyant baby. The picture was later used as the cover image for Nevermind, the second studio LP from a little rock band out of Seattle called Nirvana. Now, 17-year-old Elden is