I don't know much about crocs, but if they behave like alligators, I would not go near that water. I would rather swim with a great white than with gators.
But all things considered, this sounds like it could be something that could work out well. You only get up to 20 cents per ball if perfect, and less depending on condition, so you would need to find a LOT of golf balls. I bet you could get a lot without even diving though.
Back home we used to go digging for clams. You would use a metal rake and wade into the muddy marsh areas and dig them out at low tide. I am sure a similar technique would work for golf balls. Plus you could wack a giant eel or snake with the rake if you really had to. LOL