What happened
A pilot was operating a float-equipped airplane along the northern shore of Lake Michigan. During the flight, the pilot observed fog and lowering ceilings developing over the lake. After reporting clear air over land to a Flight Service Station (FSS), the pilot continued toward the destination but encountered deteriorating weather conditions.
Due to the reduced visibility and low ceiling, the pilot elected to perform a precautionary landing on the water. The passenger reported that the water conditions were rough at the time of arrival. Upon landing, the aircraft struck the water hard, causing the right float to dig in and the airplane to nose over.
Following the impact, the passenger was able to escape the cabin through the passenger window with the assistance of the pilot and successfully swam to the surface. The passenger attempted to return to the aircraft to assist the pilot, but found him stuck halfway out of the window and was unable to free him.