Moments after a calm-water takeoff, the single-engine floatplane stalled while in a climbing turn and impacted the water in a nose low attitude. The airplane came to rest nearly submerged with the empennage extending above the surface. The pilot and passenger were able to exit unassisted. During the mishap the airplane’s wing struts were bent and both floats were torn free from their mounts. The pilot reported that there were no mechanical problems with the airplane that contributed to the accident.