On August 1, 1997, about 2200 Alaska daylight time, a Cessna 170B tail wheel equipped airplane, N3491C, sustained substantial damage when it impacted water during an attempted takeoff from a beach on Seymour Canal, about 22 miles southeast of Juneau, Alaska, at position 58-00.0 north latitude, 134-20.0 west longitude. The private certificated pilot was uninjured. The flight was conducted under 14 CFR Part 91 in visual meteorological conditions as a personal flight. Lighting conditions were evening twilight. The pilot stated to the NTSB investigator that he began his takeoff from hard, wet sand with an estimated 800 feet of takeoff length available. When he saw the water become visible in the landing light, he applied flaps to become airborne, but did not have sufficient airspeed to fly. The airplane's right wing contacted the water, and the airplane came to rest approximately 200 feet from the shoreline, in approximately three feet of water. The pilot waded to shore, and was picked up by a passing aircraft about 1000 on August 2, 1997. The pilot stated that he weighs 180 pounds, and that there was 90 pounds of fuel on board. The passenger seats had all been removed, and there was a thirty pound pack and a ten pound rifle on board.