Tagged polar bear swims 74km

In the first conclusive evidence that polar bears can swim long distances, a tagged female swam 74km in 24 hours, between two Arctic islands in Norway.

As the bear wasn’t swimming in a straight line, the distance covered was probably closer to 100km, an average of about 3 - 4kms per hour.

ABC News: Polar bear makes 74 km Arctic swim
The World Wildlife Foundation’s Polar Bear Tracker