According to the pilot, he was planning on performing a runway landing, and had extended the landing gear. During the approach, he elected to perform a water landing, due to the 90 degree crosswind. During the water landing the airplane nosed over and came to rest inverted in the water. The pilot reported that he did not complete a second checklist prior to landing and did not ensure that the landing gear was retracted. The lower cowling was crushed aft and wrinkled, the left wing leading edge was crushed aft, and the left wing bent down. The pilot stated that there were no mechanical anomalies with the airplane.