Your snake will soak in the water when the cage is too hot or sometimes to soften skin before shedding. The water is also approximately 15 degrees cooler than the surrounding air in the cage and will facilitate thermoregulation. The water should be changed at least twice a week or more if it gets soiled or cloudy. Tap water often contains chlorine and fluoride that can be harmful to your snake. It is recommended that you at least dechlorinate tap water or bottled water.
Water softeners add too much sodium to the water.
Snakes have poor long-range eyesight and therefore do not like to be in the open. A hide is advisable for the mental health of your snake. A piece of bark or an empty box of appropriate size will suffice. Most pet shops sell decorative plastic or ceramic hides that will enhance the looks of your vivarium, but be sure they are large enough that you can safely free them in case you want to remove them from their hide. In the wild, corn snakes climb for many reasons, but in captivity climbing is not necessary.