This was a clear-cut battle of land vs. water. On land, the massive walrus was too clumsy - practically immovable to mount any opposition to the polar bear. Once, however, the fighters fell into the sea, the walrus gained the upper hand and made shishkabob out of the polar bear. Again, we witness that bigger body mass has won the day - the polar bear would have slaughtered a smaller-than-walrus seal in minutes, but here the walrus was big and strong and massive enough to endure everything that the polar bear "threw" at him, and then, once the disadvantages of the size were negated, the walrus kicked the bear's ass without breaking a sweat.