From TF2 Wiki
Water is found in many maps as a terrain feature and as a gameplay element. There are two types of water: shallow and deep. Shallow water will absorb the impact from a fall, and reveal the footsteps of Spies (which will also be more audible). It is otherwise a cosmetic part of the game.
Deep water allows a character to fully submerge and swim around. Immersion in deep water will negate the fire afterburn effect instantly, as well as the effects of Jarate. Some maps feature submerged routes into the enemy base which offer a more sneakier way to the opposing team for the attackers as they are often poorly covered in comparison to more direct entrances. Like shallow water, deep water also negates fall damage.
In addition, Engineers can construct buildings underwater just like he can do on land. Due to the low visibility of submerged objects, this provides a good strategy to place teleporters or a sentry gun for some effective surprise kills.
Remaining submerged in water for too long however, will cause the player to drown. While drowning, the player will experience a periodic loss of heath and vision trouble. To negate this, the player must reach the surface, where the health lost due to drowning regenerates over time. Standing next to a dispenser or being healed by a Medic will negate the damage caused by drowning. It is therefore possible for a player swimming next to a dispenser or with a Medic healing them to remain underwater indefinitely.
Deep water has several other disadvantages:
- Swimming in deep water will decrease the maneuverability to all classes, making them vulnerable targets for enemies who have the advantage of higher ground or more suitable weapons.
- Surfacing on the water can affect vision, making aiming difficult. To counter this, fully submerge, especially if battling an opponent underwater.
- If a cloaked Spy leaves a body of water, water will drip off the Spy for a short period, giving his presence away to the enemy. Likewise, if a Spy attempts to cloak while underwater, the bubbles they make can still be seen, also giving them away.
- Pyro's firing their flamethrower or flare gun underwater will deal no damage whatsoever. Additionally, Pyros are unable to use their airblast ability.
- The Demoman's grenades and sticky bombs will travel slower and shorter underwater due to the physical effects of the water on the projectiles.
- The Sniper cannot draw and fire his Huntsman underwater.
- The Scout cannot launch his stunball underwater.
- The Heavy's Sandvich and the Scout's Bonk! Atomic Punch cannot be consumed underwater.
- The Cloak and Dagger cannot recharge while cloaked underwater.
- You cannot taunt while underwater.
Maps with water
- 2Fort – Pool of water beneath the bridge is deep water.
- Well (CP, CTF, Arena) – Deep water channels outside the team's buildings has underwater routes connecting each team's base building to the central train house buidling. The CTF version is similar to the CP version except the route to the central building is removed with the building itself. The Arena version features a small pool adjacent to the central building which offers a quick route to the central point.
- Hydro – Shallow water in the Dam and Warehouse territories
- Pipeline – In Stage 3, a small canal beneath the payload tracks has deep water
- Ravine – At the lower side of the map underneath the tall large building, water is deep in the small aclove.
- Badlands (Arena) – Beneath the small concrete bridges to the left of the spawn rooms.
- Double Cross – deep water is beneath the drop hatches of the spawn rooms.
- Sawmill (Arena, KOTH, CTF) – Large bodies of deep water found at the Lumbershack and Waterfall areas of the map.