The water in a Doncaster quarry lake is to be dyed black to deter illegal swimming during hot weather.
Extra fencing has also been put up around the disused Skelbrooke Quarry by the landowners to prevent trespassing at the site.
FCC Environment is urging parents to warn their children about the hazards of swimming in unsupervised waters like quarries, rivers, lakes and reservoirs, and of the dangers of ‘tombstoning’.
Since this year’s summer heatwave began, seven young people across the UK have drowned, including a fatality last month at another disused quarry in Auckley, Doncaster.
The warning from the recycling and waste management company follows several recent incidents of trespass by people wanting to swim in the water at the disused quarry at its Skelbrooke site in north Doncaster.
Mark Pailing, area manager for landfill north for FCC Environment, said: “We understand the temptation to swim while the weather is warm but we would like to emphasise that swimming at unsupervised sites like this is very dangerous, as the water is still exceptionally cold and hidden rocks lie just beneath the surface.
“Sadly there are a number of tragic drowning accidents in the UK every summer.”
Following similar incidents of trespass at the quarry in 2012, the company has erected additional perimeter fencing, introduced security patrols and is now planning to dye the water to make it look less appealing.
Mr Pailing added: “Trespassing onto private land is also against the law.
“We will continue to work with the police on this issue, and anyone seen intruding on our site will be photographed and any vehicle details recorded with a view to prosecution.”
Matthew Mellor, aged 27, of no fixed address, drowned on the evening of July 21 after getting into difficulties while swimming in the lake at Hurst Plantation, near Auckley.
He was with a group of friends from the Rossington area who swam across the pool but he did not surface and his body was recovered by police divers the following day. That quarry is also on private land.