A 39-year-old woman and her four-year-old son suffered "serious, potentially life changing injuries" in speedboat accident in Padstow, Cornwall, Devon and Cornwall Police said.
A 12-year-old and 10-year-old girl suffered minor injuries in the accident.
Nick Miligan, who died along with his eight-year-old daughter in a speedboat accident in Cornwall on Sunday, was managing director at Sky Media since 2004. In a statement on its website, Sky said:
"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."
Police have named the man who was killed in the speedboat accident in Cornwall as 51 year-old Nicholas Milligan from London. He was a senior executive at BSkyB.