Some correspondents favor the bear because of its teeth, jaws and claws. It is also a good enough swimmer to have some chance of beating shark in shallow water. Sharks usually catch weakly and sick animals so would be unlikely to attack a healthy bear. Another website states that white sharks are often found in shallow water and seem to prefer eating marine and mammals instead of fish. In your scenario, the depth of water is important. Also, whether the animals are trapped in the pool or can escape.