Background
The pilot had previously completed two local flights, during which water landings and takeoffs, as well as other maneuvers, were practiced. On the subsequent third flight, the pilot performed several water takeoffs and landings.
Accident Sequence
While executing a landing, the helicopter began to roll rapidly to the right. The pilot attempted to counter the roll by applying left cyclic and up collective control inputs. However, the rotor blades struck the water surface, causing the helicopter to roll inverted. The aircraft remained supported by its floats in the inverted position.
Outcome
The passenger sustained water ingestion and was subsequently hospitalized. The pilot estimated that the wind was from the northwest at 15 knots.