On September 1, 2005, about 1700 Alaska daylight time, a wheel-equipped Cessna 206 airplane, N4991F, sustained substantial damage when it collided with soft terrain in a tidal area during takeoff initial climb from a remote airstrip, about 45 miles east of Yakutat, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) local area personal flight under Title 14, CFR Part 91, when the accident occurred. The airline transport certificated pilot and the four passengers were not injured. Visual meteorological conditions prevailed. The flight originated at the East Alsek River airstrip, and was en route to the Tanis Mesa airstrip. No flight plan was filed. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on September 2, the pilot reported that he was departing on runway 20 from the gravel surfaced East Alsek River airstrip, which is 1,100 feet long, and 10 feet wide. The pilot said that during the takeoff roll, the airplane became airborne in ground effect, but the engine power rapidly decreased, and the airplane settled into about 12 inches of water in the tidal zone of the East Alsek River. During the touchdown, the right main landing gear dug into the soft sand, spinning the airplane to the right. The propeller and right wingtip struck the ground. The pilot indicated that the airplane had flown through heavy rain in the previous four days, but he had not encountered any problems until the accident takeoff. The airplane received structural damage to the right wingtip and right wing root. The FAA's Airport/Facility Directory, Alaska Supplement listing for the airstrip states, in part: "Unattended. Runway 02-20 [has] dips and humps 8 to 12 inches entire length. Rocks on surface to 3 inches. Runway used as a road." On September 12, recovery personnel reported via telephone that sufficient airframe and propeller repairs were made to the airplane at the accident site, and it was flown to Anchorage, Alaska. On January 11, 2006, recovery personnel stated that no engine problems were encountered during the recovery process. The pilot was sent a Pilot/Operator Aircraft Accident Report (NTSB form 6120.1) on September 7, but the form was not received at the NTSB's Alaska Regional Office, Anchorage. During a telephone conversation with the NTSB IIC on December 13, the pilot reported that he mailed the form. A second NTSB Form 6120.1 was sent to the pilot on December 13, but was not received at the NTSB's Alaska Regional Office. An FAA Air Safety Inspector, Juneau Flight Standards District Office, Juneau, Alaska, interviewed the pilot and passengers. The inspector reported that the pilot told him the airplane became airborne after hitting some bumps about 2/3 of the way down the runway. The pilot said he attempted to keep the airplane airborne in ground effect, but it settled to the ground beyond the end of the runway in high grass and water. Based on his interviews, the inspector estimated that the airplane was within 100 pounds of its gross weight limit with the pilot and passengers, fishing equipment, and a dog aboard. The airplane was not equipped with oversize tires. The inspector indicated that air taxi operators in the local area only use the airstrip while carrying a reduced amount of load due to the condition of the airstrip surface.