Many people would be scared to be anywhere near a polar bear, even if they had been informed in advance that the polar bear was completely harmless and that they did not need to be worried around it. Polar bears are still very large predators, and they can essentially be harmful by accident. As such, the man in this video who actually swims with a polar bear on a regular basis appears to be especially brave and daring.
Polar bears are excellent swimmers and fighters. The polar bear in this video actually appears to be very affectionate to the man in question, demonstrating that the two of them do have something of a bond. It is possible that the polar bear would not be so loving around other people, but this may just be a polar bear who is used to people. Individuals on Facebook would be fascinated by this video.