The ability for GTA protagonists to swim in deep bodies of water was introduced in Grand Theft Auto: San Andreas, and has since been seen in Grand Theft Auto: Vice City Stories, Grand Theft Auto IV and Grand Theft Auto: Chinatown Wars.
Player interaction with water prior to GTA San Andreas
Prior to GTA San Andreas, bodies of water were little more than lethal obstacles which acted as boundaries to prevent players from reaching locked areas. In Grand Theft Auto 1 and Grand Theft Auto 2, the player is instantaneously wasted should they fall into water, regardless of whether or not they are in a vehicle. In Grand Theft Auto III and Grand Theft Auto: Vice City, falling or wading into deep water is still potentially lethal, as the protagonist will rapidly lose health if they wade more than chest-deep into water.
GTA San Andreas debuted swimming as an ability, however its contemporary Grand Theft Auto Advance, and the subsequent game Grand Theft Auto: Liberty City Stories does not allow swimming. GTA Liberty City Stories is the last game of the series thus far to disallow swimming.
GTA San Andreas
In GTA San Andreas, the player can float (in a water treading position), and swim in any deep body of water using directional controls. The player can perform a breaststroke to swim at a slow pace; holding the sprinting key or button allows the player to perform a faster front crawl. Tapping the sprint key or button rapidly adds slightly more speed.
The player can dive underwater by using the "fire" key or button while in water. This allows the player to swim deep underwater using directional controls; the sprint key or button gives the player forward movement.
Whenever the player enters water, a white bar denoting the player's oxygen appears on the game's HUD, beneath the Health and armor bars. When underwater or in a sinking vehicle, the bar will gradually empty, and, when exhausted, the player's health will be reduced instead, leading to eventual drowning; the oxygen bar is replenished by returning to the surface of the water. The player's lung capacity determines how long the player can stay underwater, and is improved both by continuously diving, and by collecting Oysters. Diving allows the player to sneak past guards undetected in some missions, and can be used to explore the waters of San Andreas, revealing other secrets.
To date, GTA San Andreas still possesses the most sophisticated swimming system in the series.
GTA Vice City Stories — GTA Chinatown Wars
Following GTA San Andreas, three games have employed a swimming feature, but all three implement simplified versions of GTA San Andreas' game mechanics, with the diving element absent.
While GTA Vice City Stories allows the player to swim, it only permits swimming for a limited amount of time, determined by a "stamina" bar which decreases as the player remains in the water. When the bar runs out, the player's health decreases, followed by drowning. The player, however, can give the protagonist infinite stamina by beating the "Beach Patrol" side mission. In GTA Chinatown Wars, the player may stay in the water for as long as they please; in GTA IV, however, the player will begin to lose health after a certain amount of time in the water.