How Does The Water Breathing Sword Style Work In Demon Slayer?

As the name implies, Water Style Breathing techniques usually end up imitating running water in some way (via Kimetsu no Yaiba Wiki). So, while it is considered the easiest style, it (like water) is also considered very flexible. Techniques such as Whirlpool and Splashing Water Flow often imitate the movements of running water to create force or move in odd angles during attacks. This makes the Water Style both strong and versatile, as users can utilize techniques (such as the basic Water Surface Slash) to perform more devastating blows, or the aforementioned Splashing Water Flow to maneuver with greater ease.

Like all Breathing Styles, the true power behind Water Style lies in the breathing patterns of its user. Without proper training, the warrior would not be able to conjure the necessary speed or force to properly apply the technique. The specifics of how Water Style's breathing techniques differ from other styles (if they do at all) are never addressed, but they are the source of both the style's power and its trademark streams of water that surround the blade during attacks.