Pierre Niesen Jr, 71, from the Pittsburgh area died of drowning and hypothermia, said William Young III, Butler County coroner.
Unionville Dive Team members recovered his body. Authorities have a tentative identification of the man.
A park visitor called 911 about 10 a.m. after reportedly seeing someone in distress in the lake about 60 yards from an access road. The caller just saw an arm waving.
Park officials got there and found fishing gear near a hole in the water. There was no sign of the man.
Drew estimate the water depth at the site to be 8 feet and the temperature about 32 degrees.