On August 5, 2001, about 1500 central daylight time, a Cessna A185F, N2904Q, piloted by a commercial pilot, sustained substantial damage on impact with water during takeoff from Crane Lake (CDD), Crane Lake, Minnesota. The personal flight was operating under 14 CFR part 91. Visual meteorological conditions prevailed at the time of the accident. No flight plan was on file. The pilot reported that he sustained no injury. He reported that one of his passengers was uninjured and the other passenger sustained serious injuries. The flight was originating at the time of the accident and was destined for Pike Lake, near Duluth, Minnesota. The pilot reported: After refueling we taxied to east end of lake (see X on map) [.] West wind at est. 12 knots. Prior to takeoff checklist completed controls tested free and correct. After aircraft on step and flying speed attained (60 kts) the right float was raised and slight back pressure we were airborne. On attempting to move control wheel to the right to level the a/c, the control wheel was jammed. I immediately suspected that the rf seat passengers knee was beneath the right side of the control wheel preventing return to neutral position. I shouted to him to move his knee but the control wheel remained jammed. The a/c continued in a left bank reaching est. altitude of 30 to 50 feet above the water. The left bank increased and we began to loose altitude despite full power. The aircraft impacted the water in approx. a 40 [degree] bank (lt) and 45 [degree] nose down attitude. We completed approx. 180 [degree] turn from our takeoff heading. ... After liftoff this happened very quickly. Probably in less than 10 or 15 seconds. At 1458, the recorded CDD wind was 200 degrees at 5 knots. The passenger stated: ... The plane was in a hard left bank making it clear that if we continued said course a crash into the water was imminent. I heard the pilot say '[the passenger's name], your knee' twice. I immediately looked down at my left knee and witnessed the left side of the control wheel situated against the inner aspect of the knee, but not appearing obstructed from movement. It never occurred to me to look at the right knee. When I looked back up I could see the inevitable about to happen and mentally tried to prepare myself for a very sudden and harsh impact. ... I honestly do not know what precisely caused the accident. I never asked the pilot if he witnessed my knee blocking the control wheel. My awareness is always on high alert when flying. I was wearing a pair of shorts that day and I did not sense any 'pressure or jamming' on or about either of my knees. The absence of any bruising or abrasion on or about the knee/upper leg makes me suspect my knees weren't the cause as well. Federal Aviation Administration Inspectors examined the wreckage. Their examination revealed no pre-impact anomalies.