Community wardens are to start patrolling Clatto Country Park in Dundee after a spate of anti-social behaviour.
It is feared someone could be killed at the beauty spot – either through drowning in the reservoir or because of persistent fireraising.
Emergency services were called to the park at the weekend after two boys got into difficulty while swimming.
And last week a blaze destroyed the old Sluice House, known locally as the Round House, followed by another fire in the woodlands.
Members of environmental group Friends of Clatto say they are frustrated at the number of incidents in the park in recent weeks.
Dorothy McHugh, secretary of the group, said: “We are despairing.
“I am appealing to Dundee City Council to take some action to prevent serious incidents that could potentially risk lives, and wanton destruction of the fabric of the reservoir and the surrounding woodland.
“Following the recent fire damage to the B-listed Sluice House, another fire was set in the woods last week necessitating attendance by the fire service.”
Dorothy says boys are swimming in the reservoir every day – into early evening.
She continued: “They are jumping from the valve tower into 25ft of water and using the life rings to swim out to the jetty that is now anchored in the middle of the reservoir.
“They congregate on the path beside the now fire-damaged Sluice House, obstructing access for visitors.
“I’ve spoken to these boys almost daily and, quite frankly, they’re just out for a bit of fun, they’ve always been perfectly polite with me.
“But the fact remains that some folk find them intimidating and instances of vandalism are increasing.
“There are now 11 separate areas around the reservoir where stones have been removed and thrown into the reservoir.
“The boys are trailing the life belts around the reservoir paths on their e-scooters.”
Dundee City Council leader John Alexander says people need to take responsibility for their own actions – and those of their children.
“It’s really frustrating that this kind of destructive behaviour continues to blight the reservoir,” said the SNP councillor.
“It’s all the more enraging when the community have been working hard to improve the area for everyone to enjoy.
“I’ve previously been in contact with Police Scotland and the council’s in-house teams around the community safety issues on site and will do so again.
“Without having someone based there 24/7, it’s a difficult one to fix.
“What we really need is for those people responsible, or where they are children, their parents to stop this destruction of a much-loved piece of open space.”
Kevin Keenan, councillor for the area, said: “I walk there regularly and have reported incidents of swimming, motorbikes, flytipping, youths on the ice and damage to the walls.
“I have requested that dog waste bins be emptied several times and I have also fished life rings out of the water.
“I am keen to work with the council and Police Scotland to try to resolve these issues before someone is hurt or worse.”
A Dundee City Council spokesperson said: “Our community safety wardens team is aware of this issue and has added Clatto Country Park to its patrol scheduling.
“The service is currently facing a number of increased pressures and continues to fulfil its obligations on a range of functions throughout the city to help keep residents safe.”