Many people will never see an Asian Water Snake due to their secretive lives in the muddy water of ponds, swamps, canals, and estuaries. As John Murphy writes in Evolution in the Mud, these snakes have adapted to spend up to 99% of their time under the water, such as having eyes and nostrils positioned at the top of the head to peek just above the water’s surface.
One of the most uniquely adapted of all Thai snakes is the Tentacled Snake, named for the duel tentacle-like appendages that protrude from its face. These appear to sense the movements of fish in an ambush hunting strategy unique to the species. Its flattened body is almost useless for crawling and thus it rarely leaves the water. Another extreme is taken by Bocourt’s Water Snake, which has developed a fat heavy body easily buoyed by the water which it also almost never leaves.
Unfortunately, these aquatic preferences have put some Asian Water Snake species in danger. The swamps and marshes of the Chao Phraya River basin have been developed by Bangkok and other cities such that two local species, Jagor’s Water Snake and Chanard’s Mud Snake, are both nearly extinct. The Mekong Mud Snake has done somewhat better as it lives in the less developed Mekong River Valley, while its close relative the Rainbow Water Snake has become a habitat generalist, thriving even in agricultural ponds and city canals, and thus is still common through south and southeast Asia.
There are a few members of the group that are somewhat more comfortable on land. The Homalopsis species, which includes the Puff-faced Water Snake, Martaban Water Snake, Jack’s Water Snake, and Deuve’s Water Snake, can be seen on both land and water around streams, canals, and even estuaries. And the most land-adapted of them all is the Yellow-bellied Water Snake, which spends as much as 50% of its time hunting frogs on mudflats and riverbanks.
Several species have adapted to salt water. Dog-faced Water Snake and Keel-bellied Water Snake are predators of the gobies (mudskippers) that live in burrows on the mangrove mudflats. A different route has been taken by the Glossy Marsh Snake, Crab-eating Water Snake, and Cantor’s Water Snake, each of which has adapted to hunt crabs and mud lobsters in unique and fascinating ways.
Though several species (like the distinctly banded Cantor’s Water Snake) are quite obvious in appearance, many can only be identified by noting subtleties in their pattern and scales. You can see how to distinguish the different species from each other at the Guide to Identifying Asian Water Snakes in Thailand.
Thanks for taking a look!
Reptiles and Amphibians of Thailand 
Got to think about this post really, I own a home in Ayutthaya on the river noi in Phak Hai. Firstly not seeing the snake is not an indication its under water. As you would be then classifying the snake as an Amphilbian (I know you are not but 99% under water to me ought to indicate that.) But I would like to redirect your attention to this thought/ Observation. Water snakes dont have to get out of the water to not be seen but they are out of the water. Get a boat especially now while the water is lower. Go around in your boat and look under the piers and jetties of peoples homes and places where boats can dock. And you will see water snakes above the waterline resting under the rafters.
You make a good point that not seeing a snake is not enough evidence to be sure you know where the snake is. Snakes have many different ways to avoid being seen.
I want to be clear that it is only certain species of Asian Water Snake that spend 99% of their time in the water. I believe the Tentacled Snake, Bocourt’s Water Snake, and Jagor’s Water Snake are examples of some of the most aquatic species.
Thank you for your reply. I was not expecting one and I will keep my eyes open and get some photos when I next see a water snake. I am likely to run into the rainbow Snake. My land is not too big its 22 Rai, Which is around 9 acres. My water front is 118 meters of which most is over grown and there are turtles of some size that haul up out of the water but are camouflaged. The land I have is inheritated and its a family holding of 212 years. The land and its previous use has channels from the river that allow the water in but it does not go out when the water ebbs back from seasonal flooding -Phak hai Gate flooding . From time to time I see the Glyphis species in the water that I release if I can catch them as they hide under the tree roots where I dont want to go. However water snakes do reside in the area of the ponds . I note that they stay just under a lip of the land that has an eroded bank and they stay above the water but below the land in the crevice. and its this that leads me to believe they must at times get out of the water. I am not an expert for this but in my years and years of study I see traits that are not published in peer review etc and there is so much for the record that needs to be addressed and Thailand is far more deficent in Data than India and its a shame. There are fish in the Noi river that identify as only being in west Myanmar and further west of that.
There are fish in the Noi river that stay deep enough in the river bed that they dont get identified anywhere and as its bony thus no one is interested in it.
I have seen from time to time a snake I just cant identify anywhere and locals tell me its this or that, but importantly its just about knowledge and understanding what I or anyone can do to preserve a habitat if the snake is in decline. Anyway sorry to disturb no need to waste your time to reply to this. Just will as the water rises soon and goes back down at the end of the year get some photos of the water snakes high and dry for you.
The tenticled snake it makes sense it would spend most of its time in water just based on its adaptation with the tenticles and they being of little use on land. In an evolutionary sense it is probably going to end up along a path of water only at some point. The Bocourt snake I have seen in the sediment at low water and it does not make a move for the river. The Jogors snake I have not seen it. But its possible there will be “Species Complex” with these animals as lines are going to be blurred.
I am sorry if I disturbed you. My land has a unique position as far as the water is concerned. As the water flows towards me. It is flowing from a 30 degree curve in the river. And as the water passes it will be meet a strategic water gate called phak hai water gate. The local regulator will in times of low water and water retention. Will hold the water back until the water crests to a height that exceeds the rice paddies before slow release. 3- 5 times a year when this happens the water rises and backs up to me that creates period flooding in my ponds that the animals rely on for ambush or just whatever they are doing. As the water channels through. My embankments only allow water to rise against them and do not over-flow. But the channels allow the ponds to fill and most of the predators are in and around there.
Good evening.
Best regards
Supparod
Thank you very much for that! As you say, there is much that is data deficient in Thailand, and the careful observations of someone who is paying close attention to habitat for a long period of time can outweigh what is claimed in books. I would greatly appreciate any photos you can get of the reptiles on your land, especially the water snakes, and any observations that you make.