text: The Vector V40R powerboat flipped over and hit a buoy in the Solent in May last year.
  The teenage son of the driver spent a month in an induced coma after suffering life-threatening injuries.
  He was saved by the "selfless" actions his father after the crash, said the Marine Accident Investigation Branch.
  But the report said no written risk assessment had been carried out and the harbour authority had not been informed of the test run.
  "None of the crew were wearing seatbelt harnesses or helmets, although this equipment was readily available as its use was mandatory when the boat was participating in organised racing events," it said.
  Simon Dredge, aged 17 at the time of the accident on 13 May, was travelling with two others and his father Peter, a champion speedboat racer.
  Peter Dredge swerved to miss what he believed was a diver's marker in the water.
  The buoys were five-litre plastic containers used as fishing gear markers, which had been laid earlier that day.
  They did not comply with the harbour authority's requirements.
  "After the accident, when the driver realised his son was probably still inside the cockpit he did not hesitate in diving back under the boat to locate and rescue him.
  "But for his swift action it is unlikely that his son would have survived," said the report.
  The MAIB said the purpose of the report was not to apportion blame, but for "the prevention of future accidents".
target: The crew of a powerboat which crashed at 100mph were not using safety equipment during the high-speed test run, a report has said.