A 16-year-old boy and a 41-year-old man have died in separate lakes at a Norfolk beauty spot, prompting warnings over the dangers of swimming in open water during the heatwave.
It is believed the man had swum about 45m out in a flooded quarry and was heading for an island when he disappeared under the water.
In another incident at the lakes at Bawsey Pits, near Kings Lynn, the teenager, who was from London but staying in Ely, Cambridgeshire, was reported missing.
Searches were launched at around 4.30pm and the body of the man was discovered about three hours later, while the teenager was found at 9.25pm.
Both were found entangled in reeds about two metres below the surface, Norfolk's Chief Fire Officer, Nigel Williams, said.
Hundreds of sunbathers looked on as the search took place and Mr Williams said officers had to prevent members of the public entering the water in their own rescue attempts.
Mr Williams went on: "It was an extremely hot day and clearly the temptation to enter the water, despite many warning signs, was too much for some.
"When we arrived there were people still swimming in the water, oblivious to what was going on.
"Swimming is banned here and the signs are there for everybody to see."
Firefighters, paramedics, police and RAF crews were involved in the search
Norfolk Police Assistant Chief Constable Nick Dean said: "People must heed the warning - you don't know what you're going into, you don't know the currents or what underwater obstacles there are.
"People were entering the water as we were attempting the recovery so that shows how, on occasions, people ignore the warnings."
Neither victim has been named.
The 41-year-old is understood to have been visiting the lake with his girlfriend and friends.
He told the group he was with that he hoped to swim to the island and was about five metres from its shore when he disappeared below the surface.
The 16-year-old was with two adults and another teenager.
A spokesman for Sibelco, which runs the disused quarry, said it was "saddened" to learn of the deaths and that it would work with police on the investigation.
"Safety is our prime concern and signs are in place to warn against swimming and diving," he said.