We all know about the seasons in the wet-dry tropics, right? There's the Wet, and there's the Dry. True, but there's also Buildup (aka suicide season - I've not experienced it but it's apparently hot, humid, yet infuriatingly it doesn't rain), and when the rain has finished, Runoff. It's called that for an obvious reason - there's so much water around from the amount of rain that has fallen, and it's all got to go somewhere... creeks, rivers, dams etcetera all continue to flow for quite some time following the last of the rains.
As the water recedes, many aquatic organisms risk becoming trapped, and desperately try to travel upstream to permanent water. At a nearby creek, just such an event has been occurring recently. In addition to the millions of fish, shrimp and crayfish, the most exciting inhabitants of the waterway are the entirely aquatic file snakes occurring there in amazing numbers, trying to cross the culvert under the road where the water flows swiftly.
File snakes are a very small family - the Acrochordidae, comprising three species. The species around here is Acrochordus arafurae, the Arafura file snake. The family gets its name from the characteristic rasp like skin - though to aid in capturing the slippery fish that these snakes prey upon. From this skin, which is loose and baggy, to its bull-dog face; its thin bifurcated tongue to the way it can hardly move out of the water (the classic analogy compares this snake with a wet sock) - this is a snake that is simply unlike any other I've ever come across.
They're almost completely harmless. Non-venomous and they don't bite. I say almost, though. Apparently, these snakes may eat catfish, and the venomous spines of the latter may pierce the snake's skin and pose a danger when handling them! I've heard that they adopt a 'fishing pose' - the tail is anchored in some tree or pandanus roots while the body and head lolls in the current, hoping to detect a fish as it brushes by seeking shelter. The low metabolism of the species means it doesn't need to surface very frequently to breathe.
Trivia: they're supposedly quite a tasty dish in indigenous culture!