Slow health drain overtime from people suffocating And/or allow certain jutsu (water element only, or fire that can cause water to boil.) to pass through. Currently its a stun with no followup, as it doesn’t drain health or chakra for the victim, and they can’t be hit by jutsu while inside the water prison. It serves as a pause button that disrupts combot flow, and has no other use, because most people don’t want a Pause button in a PvP video game, especially when it harms the user (losing chakra) while doing nothing to the enemy