The survivors of a boating accident that killed a father and daughter are battling "life threatening" injuries suffered when the out-of-control speedboat ran over them, official said today.

Nick Milligan, 51, an executive with the British television network BSkyB, was killed along with his 8-year-old daughter Emily on Sunday when they were thrown from their boat near the coastal town of Padstow, in Cornwall, England.

The boat roared out of control in ever tightening circles, striking Milligan and Emily, killing them.

Milligan's wife and three younger children were also tossed overboard in the accident and were also run over by the boat. Victoria Milligan, 39, Amber, 12, Olivia, 10 and Kit, 4, were all airlifted to a hospital.

Superintendent Jim Colwell of Devon and Cornwall police described their injuries "life threatening" and "serious, potentially life changing."

It's not clear what happened that the family was tossed into the water.

Witness Simon Lewins, a dog walker, told the BBC that the boat " kept going off in ever decreasing circles. The screams coming from the people in the water were pretty bad."

The mayhem ended when water skiing instructor Charlie Toogood was able to jump on board the boat and stop the engine, preventing it from injuring more people in the water. It is believed that Toogood managed to get a rope around the propeller of the speedboat to try to reduce its speed before jumping on board. Lewins described the water skiing instructor as a "hero."

Colwell said that "if people hadn't come to their assistance in the manner they did, I'm confident that this incident would have been far worse in terms of the overall death toll."

Colwell said that forensic experts have started a mechanical examination to determine what caused the boat to get out of control. One of the key questions they will be focusing on is why the so called "kill cord" didn't stop the boat. The "kill cord" is designed so that when the boat's driver falls from the vessel with the cord attached, it cuts the engine.

Tributes were pouring in for Nick Milligan. His brother, Max Milligan, described him as an "extremely loving father, husband, son and brother, who doted on his family." At a press conference, he said that the fact that "he and my delightful niece died in their favorite place at the end of a gloriously sunny bank holiday weekend provides us with a tiny glimmer of light."

BSkyB described him as a "a great friend and colleague for many years and his loss will be felt across our company and the industry. Our very deepest sympathies are with his family at this time."

Tim Ireland/Press Association/Landov