Oxygen Gauge

An Oxygen Gauge is a gauge that appears whenever Link is underwater without a method allowing him to breathe underwater. Oxygen Gauges have taken on multiple forms in the series. Thus far, they have only appeared in 3D main console titles.

Ocarina of Time and Majora's Mask
The first type of Oxygen Gauge appears in Ocarina of Time and Majora's Mask as a timer appearing below the Magic Meter, counting down until Link's remaining air supply expires. Once the timer runs out, Link drowns and, unless in possession of a Fairy, gets a Game Over. Link can spend an unlimited time underwater if equipped with the Zora Tunic in Ocarina of Time or if in Zora form in Majora's Mask.

Twilight Princess
Twilight Princess introduces the first actual graphical gauge to count down Link's air supply, here appearing where preceding 3D games would put their Magic Meter. The more time Link spends underwater, the shorter the brighter part of the gauge gets, and once the gauge becomes fully dark, the same result as in previous games occurs: Link drowns and gets a Game Over unless he possesses a Fairy. Much like the Zora Tunic in Ocarina of Time, the Zora Armor grants Link the ability to remain underwater indefinitely without drowning.

Skyward Sword
The Oxygen Gauge returns in Skyward Sword, taking the form of a circular meter similar to the Stamina Meter. Using the spinning charge move underwater causes the gauge to deplete faster than it normally would. Touching a poison gas bubble also depletes large sections of the gauge at a time. Unlike its appearances in previous games, when the gauge is fully depleted, Link does not die instantly but instead begins to lose health. He continues to lose health until it reaches zero. When this happens, Link dies unless he reaches an air bubble or the water's surface. The use of an Air Potion affects the gauge's depletion for three minutes: the basic Air Potion reduces the rate the Oxygen Gauge depletes, while the Air Potion + prevents the Oxygen Gauge from depleting entirely.