The aircraft was chartered to salvage gear from a burned hovercraft that was beached about one mile south of Chinitna Bay. The pilot reported that the two passengers got the gear ready to load while he held the plane off the beach by hand, trying to keep the floats from being damaged. Also, he reported that he loaded the plane while a passenger held it. After the aircraft was loaded, the pilot taxied out and began a south takeoff. However, the aircraft would not get on the step. A check of the right float revealed that the second compartment from the front was full of water. The other compartments were dry. While taxiing to a sand beach about 3 to 5 miles away, the nose of the aircraft went under the water. The occupants egressed with some difficulty. A short time later, the plane rolled over and a hole was noted in the No. 2 compartment next to the keel. One passenger stayed with the plane until rescued. The other passenger is presumed to have drowned while he and the pilot were swimming to shore.