On March 26, 1994, about 1045 eastern standard time, a Cessna U206G, N5087R, registered to Key West Seaplane Service, Inc., crashed during takeoff at Key West, Florida, while on a 14 CFR Part 91 pleasure flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the airline transport-rated pilot and three passengers received minor injuries. The flight was originating at the time of the accident. The pilot stated the aircraft felt "sluggish" as it accelerated for takeoff. After liftoff the aircraft continued to feel sluggish. The altimeter read 100 feet and the aircraft had a shallow rate of climb. As they flew near shore they encountered glassy water and a down draft from from being on the leeside of a land fill. A right turn was initiated to remain over water at which time the right float contacted the water and the aircraft cartwheeled and came to rest inverted in the water.