There are always black snakes and tigers around the water here, I'm happy enough to keep my distance, though the blacks sure love a dip and I have been surprised a few times by a few passing by. I see heaps of platypus around too as some of these gold streams/creeks happen to be good trout streams/creeks as well, they are so bad sometimes I just skip the pools they are in knowing I have zero chance of taking a fish from them.
Last time I was out Sunny Corner I jumped 2 feet seeing one of those "toe pincher" water scorpion critters near my feet, I know they are harmless but it was the biggest I have seen, round here though its the tiger leeches that will carry you away if given a chance, especially out Oberon way.
We all know about snakes, but you need to be just as wary of dehydration and heat while out prospecting, also don't forget the ******* mosquito, Ross River, Barmah Forest and Kunjin Virus are not to be taken for granted, my cousin had Barmah Forest and was never quite right from it.
On a side note I brought Malaria back with me from a trip to Papua New Guinea, holy crap that floored me, I pretty much blacked out 2-3 months of my life going through that.
I remember going to the cinema the day after coming home and passing out from the fever, woke up in hospital, my mates thought I was just quiet watching the movie until the credits rolled and the lights came on! I was fine going through customs and immigration etc, had no idea at the time.