Three teenagers have escaped unhurt after the tent in which they were sleeping was set on fire.
The incident happened in the early hours of Saturday morning at Powillimount beach at Southerness in Dumfries and Galloway.
The three youths, two aged 16 and another 17, managed to put the fire out but their tent was damaged.
In a second incident another tent being used for storage was set alight and its contents destroyed.
A police spokesman has appealed for anyone who may have been on the beach to contact them.
He said: "Both acts were totally irresponsible and could have caused serious personal harm to the occupants of the tents."