The pilot was landing on a remote tidal beach in a tricycle landing gear-equipped airplane. He stated that after making several passes over the intended landing site, he made a normal approach and landing. During the landing rollout, the nose gear stuck in the sand, and the airplane nosed over. The airplane sustained substantial damage to the vertical stabilizer. The pilot stated that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation.