The police investigation into the tragedy will focus on why the boat kept running when there was no-one on board.
All modern speedboats come equipped with a kill cord which is meant to shut down the engine in an emergency.
Simon Bagge reports on the background to the inquiry:
The widow of a man who died with his daughter in a speedboat accident in Cornwall has told of her big mistake in not using a safety device
A report into a speedboat accident off Padstow has revealed that a father and daughter died after he tried to make a fast turn.
A father and daughter were killed by their out-of-control speedboat in Cornwall after he took over the steering, investigators found.