At 1600 central time, a Cessna 182A crashed when the engine lost partial power on initial climb from Sam Riggs Airpark. The pilot and two passengers were not injured; one passenger sustained minor injuries. The pilot said he departed runway 22, a 2,760-foot turf runway, after a normal runup. At approximately 500 feet agl, the engine lost most of its power output. The pilot banked slightly to avoid an approaching tree line and initiated an emergency landing to an open grass field. The airplanes right wingtip struck the ground and the left main gear dug into soft ground. Examination of the airplanes fuel system revealed water in the carburetor bowl and both wing fuel tanks.