On June 21, 1997, at 1330 central daylight time, a seaplane equipped Maule M5C, N5643Y, sustained substantial damage during the takeoff run from a seaplane base when it ran into cattails and nosed over. The two pilots on board were not injured. The 14 CFR Part 91 flight was attempting to takeoff from the Surfside Seaplane Base, Lino Lakes, Minnesota, on a local flight. Visual meteorological conditions prevailed and no flight plan was filed. As reported in a written statement, the owner had purchased the airplane the previous day of the accident, and was seeking instruction in the aircraft to fulfill his insurance requirements. After the FAA Certified Flight Instructor and the owner had placed the airplane in the water, they taxied to the re-fueling dock of the airport. After topping off the tanks, they performed a pre-takeoff checklist and configured the aircraft for takeoff. The owner referenced the Pilot's Operating Handbook and noted to the CFI that the takeoff configuration, for takeoffs in water, was 35 degrees of flaps. The CFI responded that only 15 degrees of flaps were needed for the water takeoff. The CFI configured the aircraft, then initiated the takeoff run on an easterly heading. The owner reported, "during the takeoff run it seemed to me that we had difficulty getting on a good step situation." The pilot further said, "at the point where an aborted takeoff should have been executed, I saw him [CFI] reach for what I was certain would be the power and an aborted takeoff. Instead, he [CFI] reached for the flap handle and put the flaps at 35 degrees and horsed back on the controls so that the nose did come up, but there was no way we could avoid hitting the shore which was covered with bull bushes." The airplane contacted the high grasses, nosed over, and came to rest inverted 150 feet from the shoreline. Subsequently after the accident, the Certified Flight Instructor reported that, "it seemed to be accelerating, but was not up to speed, I then lowered the flaps to 35 degrees. I momentarily veered to the left slightly, but it was to late, and we plowed into the cattails and nosed over." The CFI further stated, "I was a little to late in aborting the takeoff." In a telephone conversation with the owner/operator of the seaplane base, he stated that the CFI elected to use a shortened portion of the lake for the takeoff run. The seaplane base owner, who witnessed the accident, further mentioned that if the pilot had steered 10 degrees from his initial heading, there would of been an additional half mile portion of the lake that could of been used for the takeoff run.