I once was paddling over here, and thought I saw an eel, so I paddled toward it, then thought it was just a stick. Next minute it swam up and onto my kayak, rammed its head into my stomach under my life jacket whilst it was climbing up onto my kayak, then jumped off the other side and swam toward the bank.
Turns out it wasn't an eel or a stick. It was an eastern brown snake, the worlds 2nd most venomous snake:
crikeymatemosaic.wordpress.com/2006/10/1...snakes-in-the-world/
I've also been sitting at the bottom of a class 2-3 rapid when a 3m red belly black snake that was sunning itself on the bank jumped in the water. Luckily it got back out before it got down to me!
Also, there are a lot of water dragons over here (a kind of lizard, not dangerous). They always sun themselves on rocks then jump into the water when you get too close. Once while paddling a river, one jumped about 15ft out of a tree and landed right on my mates spray deck, absolutely scared the crap out of him. Was one of the funniest things ever!