Deep Water is a mechanic/hazard present in the new Swamp biome, covering a very significant amount of the Swamp, presenting one of the major hazards of Chapter 2. However, traversing deep water is essential to finding loot crates and corpses.
When the Protagonist enters deep water, his general movement speed will be slowed. Attempting to sprint will provide a negligible speed increase, and cause Stamina to plummet. Actions like attacking and reloading are unaffected by Deep Water.
Enemies may hide partially or completely in the water - Swampers are specifically made to benefit from deep water in that they may hide completely, move quickly and almost soundlessly (except with rare telltale splashes), launch out from the water onto dry land while dealing damage, and evade firearms by submerging.
Some enemies will be slowed as much as or more than the Protagonist when they enter deep water, especially humanoid enemies like Savages and Mushroom Men. This allows deep water to be used to the player's advantage in some situations.
Loot in deep water acts very predictably: a large round area of deep water will spawn either a Corpse and a Locked Loot Crate, or a Corpse and Mushrooms.
If a creature dies in such a way that part of its sprite falls in deep water, that part of the corpse will be very difficult to see. The corpse can be looted as usual, but if most of the sprite is 'submerged', finding old corpses can prove difficult.