Police say that a combination of the current hot weather and open water could provide a deadly temptation for the thousands of youngsters now on their school holidays.

The warning comes on the anniversary of schoolboy Christopher Glen's death three years ago tomorrow.

Christopher 15, drowned after being sucked under the water by strong currents while playing in a notorious stretch of the River Tees, near Darlington.

Two similar deaths have occurred already this year in this region involving swimmers who have drowned in inland waters.

Andrew Cousins, 22, died in June after jumping into a deep quarry pool at Greenfoot Quarry, Stanhope, Weardale.

And Liam Robinson, 12, an army cadet from Ferryhill, drowned in May while playing in the River Wear, near Sunderland Bridge between Durham and Croxdale.

Sergeant Sgt Andy Criddle, leader of North Yorkshire police's diving team, said: "The worst part of my job is recovering the bodies of young people who thought it would be fun to swim in a river or lake.

"Quite simply, water kills."

Sgt Criddle outlined the countdown to disaster: "It's a warm day, you think a dip would be cooling and fun. Rather than going to a swimming pool, you and your mates opt for the local river or pond.

"You jump in, strike out full of energy and in no time you are away from the bank. Rivers and deep bodies of water stay cold whatever the weather, and the first you realise is when you start feeling panic.

"This is because you are going into shock.

"Because of the sudden cold, your blood goes to your vital organs. You can't breathe properly, your limbs are sluggish and, because the blood has gone away from your brain, you are not thinking too clearly.

"The final link in the chain of events is that you lose strength and drown, often not far from safety."

Police say that rivers often have unexpected currents which can sweep a swimmer to their death, while debris underneath the surface provides a further hidden danger should someone become entangled.

According to the Royal Society for the Prevention of Accidents (RoSPA) in 2001 264 people drowned in inland open waters.

Steve Jones, a spokesman for Darlington Borough Council, said: "This time of the year when it's school holidays and the weather is very warm it is tempting for youngsters to want to play in rivers like the Tees.

"It looks harmless but it is dangerous. We urge people to only swim at a properly supervised swimming pool or beach."