Police say just before 10 p.m. ET on Saturday, a man slipped and fell down a rock face in Gravenhurst, Ont., ending up in Muldrew Lake.
The people who had been with the man immediately started to search for him.
Police were also called to the scene, as were members of the OPP's Underwater Search and Recovery Unit.
The underwater search members found the victim's body on Sunday morning.
On Sunday, police identified the victim as 24-year-old Aaron Inches of Bramalea, Ont.
A post-mortem examination was scheduled to take place on Sunday.