Being an aquatic predator can sure have its disadvantages. No wonder Bruce the great white shark resolved along with his friends Anchor and Chum to quit eating fish. But every now and then, his instincts go wild when he smells a whiff of blood causing him to go into a feeding frenzy, which the Devils take advantage of in the war. Fortunately, he was strong enough to resist (most of the time) and uses his predatory instincts to help his friends. Still he's a potential danger that both sides keep an eye on.
To be fair, Bruce and his comrades feed on dolphins. And the Sharks themselves dislike humans given that some of them tend to make a tempting meal out of the fins of their kind.