Toronto police resumed their search Sunday for a man who disappeared after falling off a boat in Lake Ontario Saturday night.

Officers say they are treating the search as a missing persons case, and focusing the hunt on an area about three kilometres south of Humber Bay, where the man fell into the water at about 7:40 p.m.

"It’s a very large area and due to the timeframe that it happened, it's almost 13 hours ago now, and due to the current in the Humber River, it’s going to make it much more difficult," Sgt. Gerry Klunder said Sunday morning.

The man, believed to be in his twenties or early thirties, was attending an event on the Northern Spirit Yacht when he fell into the water.

Jim Nicholson, the head of yacht owner Mariposa Cruise Line, expressed his sympathy for the man’s family on Sunday.

He said the cruise line followed protocol during the incident and is cooperating fully with police.

"We have been around for 29 years and we have never had an experience like the one we had last evening," he said.

Nicholson said there were 427 people attending the party on the three-storey yacht on Saturday, as well as 19 crew members and 10 security guards.

He said the boat was licenced to carry 550 people.