A Devon and Cornwall Police spokesman said officers were called to the scene of a speedboat accident near Padstow.
The spokesman said:
It's still an ongoing incident and we are working alongside the coastguard and ambulance service.
A father of four who was killed in a speedboat accident along with his eight-year-old daughter doted on his family", his brother has said.
Two people have died and another four people have been injured in a speedboat accident while on holiday in Cornwall.