On July 29, 2006, at 1514 eastern daylight time, a Cessna 208 amphibian airplane, N415GA, registered to Hampton Island Aviation LLC, operating as a 14 CFR Part 91 business flight, collided with a berm on initial take off climb in the vicinity of Riceboro, Georgia. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage. The commercial pilot and five passengers reported no injuries. The flight was originating from Harvest Lake, Riceboro, Georgia, on July 29, 2006, at 1514. The pilot stated the take off area on the lake is 2,200 feet long. He computed the take off distance at 1,990 feet. He completed a preflight inspection and engine run up and no anomalies were noted. He water taxied the airplane to the start point and initiated the take off by increasing power. The airplane did not rotate at the planned take off point so the pilot applied aft pressure on the control yoke. The airplane became airborne and struck a three foot tall berm and collided with the marsh coming to a complete stop. The pilot stated there were no mechanical problems with the airplane and that he failed to attain the proper takeoff point resulting in the collision with the berm on initial take off climb.