The mysterious message reading ‘help’ on a West Coast beach has been solved.

The sign was spotted by a chopper flying over Lake Ahaura last week.

The Greymouth Star reported the incident was “a prank by children”.

A “mortified” father had contacted police after reading media reports.

The Greymouth Star reported that Senior Sergeant Brent Cook said a local family had been boating on the lake and the children thought the sign would be a great joke.

“Dad is taking appropriate action.”