Croc is looking for a fight, and the Dark Knight is going to give him one. Since this is the first real boss of the game it takes things easy on you.
Croc is going to occasionally try to throw things at you, but they're easy to dodge or just hit by quick-throwing batarangs to blow the containers up on his toothy head. He'll sometimes try to bite your face, but it's not difficult to pound a button to get out of the situation.
Just beat on him for a few minutes and you're on your way to putting him back in his place.
For more tactics here's our full Batman: Arkham Origins boss guide!