Police will carry out night patrols with sniffer dogs in one of south Wales' most popular parks following vandalism.
Equipment at Ynysangharad Park in Pontypridd, Rhondda Cynon Taf, is being damaged by vandals after dark.
In the latest incident, a wooden fence around the swimming pool was smashed with debris thrown into the pool.
South Wales Police said officers would now patrol at night to prevent further attacks.
Insp Lee Porter, head of Pontypridd's neighbourhood policing team, said: "Ynysangharad Park is a wonderful facility not just for the people of Pontypridd but for those all over south Wales.
"Unfortunately a minority feel the need to climb the fence after the gates have been locked and cause criminal damage which is unacceptable.
"The park already forms part of our daytime patrols but from now on it will be included in our night time duties.
"Our colleagues in the mounted section will be exercising their dogs in the park so anyone in the park at night might very well come across a police dog.
"I would ask parents to speak to their children about where they are going at night and to stay out of the park otherwise they might get a lift home in a police car."
Police said the outdoor swimming pool was targeted at the weekend in the most recent vandalism.
Attempts were also made to start the electric waterslide, causing damage to the control panel.
While there have been problems at night, South Wales Police said there had been a "significant decrease" in daytime anti-social behaviour over the past 12 months following work by officers and Rhondda Cynon Taf council.
Anyone with information about damage in the park is asked to contact Pontypridd police station on 101 or Crimestoppers anonymously on 0800 555 111.