A 12-tonne yacht moored in the canal basin at Gravesend, Kent, has been seriously damaged by fire.
The Kent Fire and Rescue Service inshore boat was called to the yacht just after 0230 BST on Sunday, a spokesman said.
He said the emergency call came from a member of the public who saw the boat on fire.
Fire crews spent nearly four hours putting out the fire but the yacht has suffered 70% damage, he added.
A fire officer was still at the scene on Sunday morning to liaise with Kent Police, who are investigating.
The cause of the fire is not known.