Two girls, aged 10 and 12, involved in yesterday's speedboat tragedy in Padstow, Cornwall, both have minor injuries and are "recovering well", Devon and Cornwall Police has said.
Their father Nick Milligan and eight-year-old sister were killed in the accident.
A 39-year-old woman and her four-year-old son suffered "serious, potentially life changing injuries".
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 father who died in a family speedboat tragedy in Cornwall has been named by police as TV executive Nick Milligan.
He was killed along with his eight year-old daughter in the accident at Padstow yesterday.
Mr Milligan's wife and four year-old son are tonight in hospital where they're said to have life-changing injuries.
Steve Hardy reports:
Sky have released a statement after it was announced that Nicholas Milligan, an employee at BSkyB died in a speedboat accident in Padstow.
– Sky statement
Everyone at Sky is deeply shocked and saddened to learn of the tragic accident involving the Milligan family.
"Nick has been 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."
Andy Hurley from RNLI says emergency services response was outstanding.
Police are expected to release more details after a speedboat tragedy in Cornwall in which a father and his eight year-old daughter died. It happened yesterday in Padstow.
This is amateur footage of the speedboat circling after the family fell overboard at Padstow yesterday
The chief examiner at the Royal Yachting Association (RYA) has described what happened in Padstow yesterday as the "worst possible scenario". Richard Falk says that fitting a kill cord to vitually all small power-driven craft is standard practice by manufacturers.
He said it was possible for a driver of a boat to connect the kill cord to the throttle so that the engine works but then not to connect it to him or herself.
"It is possible for the operator, the driver of the boat, to connect the kill cord to the throttle so the engine will work but they don't connect it to themselves. If they then move away from that throttle or steering position the engine won't cut out.
If you fall over board and there is no-one else to drive the vessel, the vessel can obviously run off and hit somebody else and cause damage that way.
– Richard Falk, Royal Yachting Association
Alternatively it can leave you in the middle of the water with no assistance if it sets off in a straight line.
Or the worst case scenario is that the vessel goes into a turn and keeps going back towards you, where it keeps circling around a focal point. The whole idea of the kill cord is to prevent any of these situations occurring.
This was a video shot by a member of the public of the rescue operation at Padstow
A 39-year-old woman, a four-year-old boy and two girls aged 10 and 12 are still being treated at Derriford Hospital in Plymouth. They are described to have a range of injuries, some of which Devon and Cornwall Police are describing as "life threatening" as well as "life changing".