As with all living creatures, snakes need water to stay alive. If they don't get water, they will dehydrate and eventually die. Snakes definitely need water, so they somehow need to get it into their system. Now, they don't drink it as we perceive drinking. Certain species of snakes need less water than others. Some take water from a pool or river while others will take it through small holes on their skin.
People can watch their pet snakes to see if they need water or if they are hydrated enough. You can check it by tenderly grabbing the skin on a snake's neck – if the skin "elastically" goes back as soon as you let go, the snake isn't dehydrated; if, on the other hand, the skin stays loose without going back right away, this is a sign that the snake is dehydrated and it needs to get some water.
Some snakes actually put their mouth into the water and it seems as if their jaws are moving in a motion to get the water into the body. Actually, what a snake is doing is engaging in capillary activity. Water gets into their mouth and then through small folds on the skin of the lower jaw it will get soaked into the body and travel to the snake's stomach.
Certain researchers have discovered that boa snakes suck the water into their bodies through a small hole in the mouth – just as if it was drinking water through a straw. There is no actual proof that this activity is classic suction. Instead, it seems that skin in the lower jaw opens slightly in order to enable free passage for the water to go toward the stomach and intestines.
This is a way for the water to gets into the snake's system because snakes don't have organs that would enable them to get water into their body as mammals do – their tongue is simply too thin (and sheathed) to perform the function as it does with mammals. Also, a snake doesn't have the ability to move its head back to get the water down the throat as people can.
Scientists say that the mentioned folds in the skin of the jaw function as small tubes that sponges also have and that they transport water into their body through classic capillary activity. Muscles in the intestines then transport water toward the snake's stomach. Scientists consider this activity a real masterpiece of nature with all the restrictions snakes have to get water into their system and stay hydrated.
For more information about whether snakes drink water or not, go to my Snake Removal - How to Get Rid of Snakes home page.