Whitehaven Coastguard was called out after reports that a jet skier was being ridden recklessly at St Bees.
A spokesman said the reckless riding had endangered swimmers in the sea – many of whom were forced to exit the water for their safety.
When the members of the Coastguard team arrived, the jet ski had left the area and swimmers had returned to the sea.
The spokesman added: “We would like to take this opportunity to remind pleasure craft user they must comply with the International Regulations for Preventing Collisions at Sea.
“You could be prosecuted if you’re involved in a boating accident and haven’t followed the regulations.
“We would urge all pleasure craft users to be considerate of other water users and hazards, ensuring they handle their craft safely and responsibly in the interest of everyone’s safety.
“It would only take a moments lapse of concentration, or unawareness of other users, for this to become a serious or fatal incident.
“Our thanks to the first informant, who was an off duty crewman from RNLI Blackpool holidaying in the area.”
