OPP said a body has been recovered at the Guelph Lake Conservation Area.
They believe it is that of the swimmer who went missing Sunday afternoon.
Wellington County OPP said a coroner arrived at the scene and has scheduled a post-mortem.
They said the identity of the deceased is being withheld until they have notified next of kin.
Investigators said a swimmer was reported to be in distress off the main beach at the conservation area around 5 pm.
READ MORE: Five people hospitalized following Elgin County crash, OPP say
OPP, the Guelph Fire Department, the Grand Valley Fire Department, OPP Aviation Services, and the OPP Underwater Search and Recovery Unit arrived to assist with the search.
The main beach at the Guelph Lake Conservation Area remains closed until further notice, and the public is being asked to avoid the area.