Swim

Swimming is an inherent ability of all player characters, and some mobs, which allows one to travel in and under water. Swimming is slower than running, but faster than walking.

When your character is in the water, press the sit key will dive deeper, while pressing the jump key will surface. You can hold the left mouse button to look around. You can hold the right mouse button and then move your mouse up and down to change your swim direction. Moving your character forward or backwards will then make them swim in the direction you have chosen. As a ghost or while water-walking, pressing both mouse buttons and angling the camera downward will allow your ghost to swim.

When underwater, a character begins to run out of breath and may drown. Resurfacing will allow the breath bar to slowly refill. Some underwater places have 'pockets of surfacing air' visualized as underwater air bubbles coming from cracks in the crust or barnacle-like models - you can stay there and fill your breath bar. These pockets are usually places in places related to some underwater quest. Deeper waters (such as around the continents) will fatigue characters, whether they are above or below the surface. When either the breath bar or fatigue bar expires, characters begin to take damage. Both drown and fatigue damage can be healed, allowing the character to go on for a little longer.

Ghosts do not have to breath underwater, but are still affected by fatigue and can be killed a second time.

Mounts
There are swimming mounts that are specifically desgined to increase swim speed, with the caveat of only being truly useful in water. Many are gained through fishing or fishing up a currency, looting a rare, as a rare drop, or as a quest reward. Examples include:


 * Sea Turtle (mount)
 * Darkwater Skate
 * Reins of Poseidus
 * Surf Jelly
 * Vashj'ir Seahorse (Vashj'ir only)

Underwater Walking
Underwater walking is a new movement mechanism introduced in Cataclysm that allows the character to function as if he/she is on land when standing or walking on the seafloor. This includes water breathing, the ability to eat or drink while on the seafloor, the ability to mount on the seafloor, and increased movement speed while not mounted and walking on the seafloor.

Methods to breath longer underwater

 * Several items, including Hydrocane, Mastercraft Kalu'ak Fishing Pole, Deepdive Helmet and Band of Icy Depths allow underwater breathing while equipped.
 * Alchemists can brew Elixir of Water Breathing and Elixir of Greater Water Breathing.
 * Warlocks have a castable Unending Breath buff.
 * Often, underwater quests will provide a summoned item that will provide underwater breathing.
 * Certain quest rewards, such as Nagrand Cherry, allow short underwater breathing buffs.
 * Druids in their Aquatic Form can breathe underwater. Switching to Aquatic Form after an underwater fight is a convenient way to take a breath before the next fight.
 * Undead players have no need to breath, due to their Touch of the Grave racial trait.

Methods to bypass the need for swimming

 * Shamans (at level 28 Water Walking), priests (at level 34 Levitate) and death knights (Path of Frost at level 61) get spells that allow them (and possibly nearby party/raid members) to walk across the water surface — however, taking damage breaks the spell.  At level 69, Beast Mastery hunters can tame water striders to use the Surface Trot exotic ability.
 * While in ghost form all characters can intrinsically water-walk. If you want to dive into the water while walking over it, tilt your camera to start pointing down into the water and 'go down'. To step onto the surface of the water while submerged and having cast a water walking spell, hold the jump button. Characters can jump to get back on top of the water while mounted, however the bigger/taller mounts cannot jump high enough, and will fall through.
 * At lvl 60 and upwards, characters with the appropriate riding skill can fly over water with flying mounts. Many regular-sized flying mounts can be mounted (and swam under the surface) while in water. As of Patch 5.4.0, drake mounts and nether ray mounts can also swim.
 * Lvl 90 characters can purchase the Anglers Fishing Raft for themselves and the Reins of the Azure Water Strider for all their mount-usable alts from The Anglers.

Additional notes

 * Swim speed, unaffected by anything, is just a bit over two-thirds the speed of running.
 * Regular mounts are able to swim, although they travel no faster than an unmounted player. Originally, entering water while on a flying mount would dismount the player.
 * You can escape combat from some mobs if they can't swim; for example, a wolf.
 * You can escape combat from some swimming mobs because they can't leave the water; for example, a threshadon.
 * In the event of an encounter where you do use the transition between land and sea to break a fight, the mob in question will evade but remain in combat with you. It should, in most cases, reset within a few seconds.
 * Some amphibious mobs can pursue from land into the water and swim after you or from water to land and run after you. For example, a murloc. Unless you have a method of reliably swimming fast while in combat, it would be a very bad idea to try escaping such mobs by swimming.