Here along the SoCal coast from Huntington Beach to Ensenada, the most popular in-the-water camera for board surfers, long boarders, kayakers, and shallow scuba divers is the remarkable nikon aw-100 - used by major commercial film folks as well for the same purposes - easy to mount and use on the front of a board:
http://www.nikonusa.com/Nikon-Produc...PIX-AW100.html
Otherwise, from beach or shore vantage points use any great long lens - 35mm film camera digital cam combination that can get you to equivalent 400mm - 600mm focal lengths.