The 16-year-old was last seen struggling in the water at Salford Quays, Greater Manchester, at around 6.15pm on Saturday.
Police, fire and ambulance services were called and a search was mounted.
A boy’s body was located and recovered by specialist divers overnight.
Although formal identification is yet to take place, the body is believed to be that of the missing 16-year-old.
His family is being kept updated, and supported by specially-trained officers.
A general view of Salford Quays
Wiki Commons
Greater Manchester Police (GMP) said inquiries are continuing but detectives from Swinton CID are at this stage confident that there are no suspicious circumstances, and a file is being prepared for the coroner.
Detective Inspector Joanne Johnston, of GMP, said: “Yesterday evening’s events are nothing short of devastating and my thoughts are with the friends and family of the young boy who lost his life in such awful circumstances.
“We are doing all we can to support the boy’s family at this incredibly difficult time, and we are focused on ensuring they get the answers they deserve as to how this tragedy occurred.
“From our inquiries so far, we are confident that there are no suspicious circumstances and that this is such a sad reminder of the dangers of entering open water, whatever the weather.”
As the record-breaking heatwave begins, GMP said people need to avoid being tempted to cool off in reservoirs, rivers, canals or ponds.