A friend's lab was sniffing a crab and the crab clamped on to his his nose. The dog headed up the beach on a dead run, howling all the way. The crab finally let go, dropped to the ground and assumed his combat stance with his claws at present arms ready for another go round. The dog started circling the crab and the crab kept turning. Finally the lab started circling fast enough to get ahead of the crab and grabbed the crab by the back of it's shell and preceeded to rip it apart and eat almost the whole thing.
We were heading up the beach to grab the lab but by the time we got up there the dog was just grinning with a look of satisfaction with crab bits all over his head. His nose was bleeding a bit but he wasn't in as bad a shape as the crab.
He never messed with a crab again.