Worried police fear youths are risking their lives by diving into open water near Conisbrough during the recent hot weather.
Officers have confirmed they have been told of ‘young people’ going into the River Don off Burcroft Hill in Conisbrough.
It is one of a number of reports across South Yorkshire which have been received to the authorities in the last few weeks.
A spokeswoman for South Yorkshire Police said: “As temperatures continue to rise, it is essential to be aware of the dangers that rivers, lakes and reservoirs can present.
“Places like rivers, lakes or flooded quarries are completely unsuitable for swimming as they hide a number of hidden dangers.
“River flows can be unpredictable and water is often deeper, colder and faster than expected. People should enjoy water safely in swimming pools or safer, specialist facilities instead.
“We urge people not to put their lives at risk by being tempted into open water during the heat.”
Police say the dangers of open water are:
* The water can be much deeper than expected.
* Rivers, lakes, canals and reservoirs can be colder than expected
* Cold water dramatically reduces people’s ability to swim.
* There may be hidden currents, which can pull swimmers under the water.
* Hazards like pieces of rubbish or reeds under the water can trap or injure swimmers.
Over 400 people die in the water every year in the UK, and SYP is urging people to follow some basic rules to stay safe.
Manvers Lake near Wath has been among the areas hit by tragedy in the past.
Swinton Comprehensive School pupil Phillip Law, from Kilnhurst Road, Rawmarsh, was pulled from the water by the emergency services after a huge two-hour operation involving scores of rescue vehicles in 2010.
But an inquest later heard he had drowned, despite the efforts of two school pals who desperately tried to rescue him before he slipped beneath the water.
Phillip and two pals had swum out to an island in the middle of the lake, leaving behind a fourth boy who declined to go with them.
Coroner Nicola Mundy later told an inquest she was convinced the cold water had been the cause of Phillip’s difficulties.
“He entered what, in my view, is a treacherous stretch of water, with little or no appreciation of the critical effects a drop in temperature can have on the body,” she said.
It was not the first time tragedy has struck at the Manvers lake, which sits on the former Manvers Colliery site.
In 2005, 18-year old Adam Peterson also lost his life after trying to swim out to the same island, and a boy drowned there 10 years before that.
Schools have attended water safety sessions at the lake since.