Ice Breakers member Bob Stewart says the unusually warm, roughly 50-degree air made it "almost like a summer day" - by these swimmers' standards, anyway.
About two dozen Ice Breakers members immersed themselves in the roughly 45-degree water.
An hour later, a few hundred people joined the Polar Bears' plunge. First-timer Russell Downes called it "one heck of an ice bath."
The Polar Bears' event is a fundraiser for Camp Sunshine, an organization that helps children with life-threatening illnesses.
The Ice Breakers aim to promote human and environmental health.
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