This technique traps a target in a sphere of water; the water can either be drawn from the surroundings or expelled from the user's mouth. The water that the sphere is made from is noticeably heavy, which restricts the target's movements and can make breathing difficult. As such, those trapped within the water prison cannot ordinarily escape on their own. Neji Hyūga was able to free himself by simultaneously releasing chakra from all of his tenketsu, destroying the prison. In Akatsuki Hiden, Kisame Hoshigaki escaped by increasing the volume of water within the prison beyond what it could contain, causing it to burst.
In order to maintain the prison, users must stay in contact with the sphere, typically by keeping an arm submerged within it. For this reason, water clones can be used in combination with water prisons, either by having the water clone attack other targets while the user maintains the prison, or by having the clones themselves form the prisons, leaving the user free to act. In cases where a water clone forms the water prison, the water of the clone's body can be used as a source for the prison. In the anime, this contact is shown to not be necessary, allowing users to trap targets from a distance.
The water prison's usefulness has caused it to be adapted for other purposes. It can be stored in scrolls, trapping anyone who tries to read their contents without permission, though these prisons don't place as much of a restriction on the victim's movements. Alternatively, users can confine themselves within a water prison, thus preventing opponents from reaching them.
- In the anime, Umibōzu's entire body is composed of water, which allows it to drown its opponents inside it, thus leading Amachi to refer to it as a "Moving Water Prison Technique" (動く水牢の術, Ugoku Suirō no Jutsu).