Drinking water in Ark Survival Evolved is easy once you know how. The simplest way is to dive into the water and go for a short swim. In a few seconds, your character’s water is filled automatically. The better way to drink water is to stand in the water and hit the use button (E key - PC, Y - Xbox, triangle PS). If you are in the right spot you will take a drink and your water will be filled instantly. You can even do this on the run, if you are being chased by one of Ark's aggressive dinos. Not every little river allows you to drink, or you may have to move around until you get to the correct spot. Your character's water will also be filled when it is raining.
Soon you realize you need to craft a waterskin, so you can venture away from beaches and rivers. To fill the water skins, jars, and canteens, stand in the water, highlight the water skin, and hit the use key/button, and it will instantly fill. You can do the same while in the rain, but you can't use it while swimming. The next upgrade is to set up a water irrigation system, which I will describe in another post.