Police continue to search for a 20-year-old man who went missing Sunday after the boat he was on capsized in Lake Simcoe.

The man was sailing with two Toronto men when their fishing boat overturned, York Regional Police said Monday.

An off-duty officer found the two Toronto men, 73 and 48, stranded in Cooks Bay around 2:20 p.m. Sunday, roughly two hours after the incident. He called 911, police said.

The men were taken to hospital and treated for hypothermia.

Meanwhile, police boats, aided by a search-and-rescue Hercules aircraft dispatched from CFB Trenton, searched for the third man.

Emergency crews have yet to locate the 20-year-old, a resident of Georgina. He was last seen wearing a black hooded sweatshirt with white designs, jeans and a baseball hat.

Police are asking boaters to stay away from Cooks Bay near Ravenshoe Road as they continue to comb the waters for signs of the missing boater -- a search that also involves the police's underwater recovery unit.

They are also urging resident along the eastern shores of the bay to keep watch on the shoreline and their property.