How does Water style function in naruto?
In the Naruto-verse, chakra can be converted into all forms of nature. That's the logic of the Anime. A user with affinity to any chakra nature can create that element using his/her chakra. Water release is no exception. Ninja's with an affinity to water nature type can use their chakra to create water. However, the amount of water they create depends on how much chakra they have.