Flying across from Darwin (YPDN) to Karumba (YKMB) The Gulf of Carpentaria.
I went there in the mid-90's. There were "no-swimming" signs in the rivers and on the beach. Apparently, the Tiger Sharks and the huge saltwater crocodiles ("salties") literally have fights in the surf. Unfortunately, I never got to see one of these fabled contests (the crocs always win - mean muthas them salties)