The airplane collided with water following a loss of engine power. According to the pilot, he picked up an advertising banner at a private airport and proceeded at 1,000 feet AGL to the beach. Upon arrival at the beach, he turned to a 250-degree heading and descended to 500 feet AGL. The pilot stated that he switched to the right fuel tank, which was full, and experienced a power failure. He switched back to the left fuel tank but could not restore power. He landed in about two feet of water, substantially damaging the airplane. Examination of the airplane by an FAA inspector found that the pilot had departed the private airport with 5 gallons of fuel in the left tank and 18 gallons of fuel in the right tank. When the pilot switched tanks, the engine stalled. His attempts to restart the engine were unsuccessful. The engine was not equipped with an electric starter and it had stopped wind milling. The pilot conducted a forced landing onto the beach and did not drop the banner. Damage to the airplane consisted of the tail section and damage to the airframe structure. There were no mechanical problems reported by the pilot or discovered during the post-accident examination of the airplane.