Water
From Inkipedia, the Splatoon wiki
Water is a terrain feature in Splatoon.
Description
Water is a liquid that Inklings can die from. This may be because the ink that the inkling comprises off washes out. Inklings cannot touch water otherwise they will drown.
Use
In a few of the multiplayer mode stages, water is used as a hazard to kill players that fall in.
Water can be found on some levels of Hero Mode such as Propeller-Lift Playground as a hazard to Agent 3.