The coast guard says in a statement that a lookout on the Cutter Neah Bay spotted the 25-year-old man walking on the lake Thursday morning, 2 1/2 kilometres from Ontario's Seaway Island.
The coast guard says the 42-metre icebreaker sent a crew on foot to check on him.
It says the crew questioned him, treated him for hypothermia, and "assisted him aboard the cutter."
The coast guard says the 25-year-old U.S. citizen wasn't dressed for conditions on the lake, had no flotation gear and no form of communication.
It says the cutter docked at Algonac, Mich., where emergency medical workers treated the man.
The U.S. Coast Guard also released video of the rescue:
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