Emergency services were called to Ponden Reservoir near Keighley at around 5.50pm yesterday (June 16).
The major search involved the police, fire service, National Police Air Service and specialist police divers.
The body of a 27-year-old man from Blackpool was recovered from the reservoir just before 10pm, officers said.
His name has not been released.
Det Chief Insp Andy Farrell, of Bradford District Police, said: “This has been a tragic incident in which a man has lost his life and I would like to remind all residents in and visitors to West Yorkshire of the extreme dangers posed by swimming in or entering open water not designated for such use.
“Such water can be very cold, even in the summer months, and people suddenly entering cold water are susceptible to hyperventilation, which could result in the body going into seizure.
“Our thoughts are with the victim’s family and officers are working to support them as our inquiries continue.”
Investigations into the incident are continuing.
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