If you want to see a croc, just go walking near the shallow water of the top half of the country's coast. You won't see the croc for long, and it will be the last thing you ever see, but it will be up close and very personal.
Seriously though, you don't go to see salt water crocodiles in the wild or even go near any body of water on the northern coast. If you can see one with the naked eye in the wild, you're already too close. They're extremely fast, extremely aggressive, and the males get up to 6m / 20ft long and 1000kg / 2200lb. They are very much a zoo only thing.