What happened
The pilot initiated a takeoff attempt with a seaplane but aborted the maneuver shortly after beginning the roll. The abort was necessitated by a mechanical issue where the pilot seat slipped aft during acceleration. Following this interruption, the pilot did not back-taxi the aircraft to reposition it properly before commencing a second takeoff run.
During the subsequent attempt, video footage captured by a passenger shows the seaplane accelerating on the step of the water. As the aircraft gained speed, a passenger noted that the water appeared shallow. Despite this observation, the seaplane continued its forward momentum and struck a sandbar located in the middle of the river.
The impact caused the seaplane to come to rest inverted in the shallow water. No further details regarding injuries or specific damage extent are provided in the source text.