Well, this all depends on the setting of the battle. Because, obviously, a shark isn't going to last too well on land [which is obviously where I've set this battle, because the bear's got a fairly easy victory: it wasn't so easy that the bear got cocky].

Whereas, in the water, the shark would have the advantage. The bear would drown or get eaten quite easily.

On land, the shark would probably get tired and dry out and die if the bear just waited long enough. Also, the bear could run away and there wouldn't be much the shark could do about it. Go Winnie!