The pilot was departing from a remote tidal beach in a tricycle landing gear-equipped airplane. The pilot reported that during the takeoff roll the airplane hit a bump, and it became airborne prematurely. As the airplane settled back to the ground, the left main wheel contacted the water, which pivoted the airplane into the tidal surf. The nose wheel collapsed, and the airplane nosed down, sustaining substantial damage to the left wing and fuselage. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.