An accident investigator has told the inquest into the deaths of Nick and Emily Milligan in Padstow that Mrs Milligan was steering the boat into harbour for a break.
But Mr Milligan and their four children wanted to go for another ride. Mr Milligan grabbed the wheel and the throttle.
Captain Mike Evans told the inquest in Truro that the boat went from idling speed to full throttle. He said it went to the right and suddenly and violently rolled back and threw the family of six into the water.
The out of control boat circled on full power, hitting several members of the family.
This amateur footage shows the speedboat circling.
An accident investigator told the inquest that since 2005 there had been 21 accidents with small high speed boats in the UK where the kill cord had not been used.
The kill cord is a safety device which cuts the engine in an emergency. Seven people had died and 12 injured.
Captain Mike Evans, from the Marine Accident Investigation Branch, said the use of a kill cord in fundamental and should be second nature for powerboat users.
A doctor has told an inquest today how a mother who lost her leg in a speedboat accident in Cornwall last year told her 'I've lost my husband, my life is ruined and I've lost my leg'.
Dr Susan Mann, who was on holiday at the time, was on a boat trip when a family of six were thrown from their speedboat in the Camel estuary in Padstow.
Nick Milligan and his youngest daughter Emily died.
Victoria Milligan was treated by Dr Mann before she was taken to hospital Dr Mann said Mrs Milligan was cold and lost a lot of blood.
The inquest will continue in Truro today into how a father and his eight-year-old daughter died in a speedboat accident in Cornwall last year.
Nick and Emily Milligan lost their lives in Padstow when the family of six were thrown out of their boat.
It circled out of control at high speed, hitting them while they were still in the water.
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 deviceRead the full story ›
The inquest into the deaths of a father and daughter who were killed by a speedboat in Padstow begins today.
Six members of the same family were thrown from their boat in May last year.
The boat circled out of control, killing Nick and Emily Milligan.
A woman has described how she discovered her husband had been killed in a speedboat accident in Padstow.Read the full story ›
Celebrity chefs have come together to produce a cookbook to raise funds for Padstow Christmas Festival.Read the full story ›
A man has died after a diving accident in Cornwall.
The 63 year-old was with friends but got into difficulty off Trevose Head near Padstow yesterday afternoon (Sunday).
He was pulled out of the water and airlifted to the Royal Cornwall Hospital in Truro, where he was pronounced dead. Police are investigating.
A woman who lost her husband and daughter in a speedboat accident in Cornwall has started a charity cycle ride through the county today.
Victoria Milligan, who lost a leg in the accident, is raising money for the Cornwall Air Ambulance and the RNLI.
She and her family were on holiday in Padstow when they were thrown from their boat in May last year.
Her husband, Nick Milligan, 51, and their daughter Emily, eight, died in the incident. An investigation had found that the lack of the use of the boat's kill cord was part of the reason for the accident.
Mrs Milligan, from Wandsworth, south-west London, has urged other boat users to be vigilant with safety and wear a "kill cord" at all times.