Water

Water is a terrain feature in Splatoon.

Description
Water is a liquid found in many stages and Octo Valley missions that causes Inklings to dissolve when touched, forcing them to respawn.

"One of our interns recently saw a squid guy fall into a creek during a Turf War, and guess what?! The squid dissolved! This suggests that these creatures can’t maintain a solid form when submerged in water. Does this mean that they’re actually made of liquid?"

- Official Splatoon Tumblr

Use
In a few multiplayer stages, such as Arowana Mall, water is used as a hazard to splat players who fall in. It is often placed strategically under grated walkways and platforms, so that players who become squids while on said platforms are forced to respawn. Water also surrounds Saltspray Rig and Bluefin Depot.

Octo Valley
Water can be found on some levels of Octo Valley such as Propeller-Lift Playground as a hazard to Agent 3.