The report of a missing swimmer at Sawyer's Pond came about 8:15 p.m. Tuesday.
Witnesses told Gem County Sheriff's deputies that it had been about 15 minutes since they had seen the man swimming from one end of the pond to the other, and back.
Deputies found no sign of the swimmer when they arrived.
The victim was later identified as Joshua David Shaw, 34, KIVI-TV reported. Alcohol may have been a factor in the death, the TV station reported.
The Gem County Sheriff's dive team, deputies and fire department seached the lake and found the man near the bottom of the pond about 10:22 p.m.