- "Swimming for too long will drain one's energy, and eventually one will sink. Watch the round icon in the bottom-right while in the water. This is one's swim timer."
- — Sturgeon
The Oxygen Gauge appears as a timer under the Magic Meter, counting down until Link's remaining air supply runs out. Should the timer run out, Link will drown, unless he has a Fairy in a Bottle. However, if Link is wearing the Zora Tunic in Ocarina of Time or the Zora Mask in Majora's Mask, the Oxygen Gauge will not appear as he will never drown with this gear equipped.
The Oxygen Gauge, referred to as a swim timer, appears when Link enters deep water as a blue and white orb in the bottom right corner of the screen, and will slowly drain as long as Link remains in the water. As Link is unable to dive underwater, the gauge serves only as a limit to how far he can go from land, likely to prevent him from visiting other islands prematurely. If the gauge depletes while Link is swimming from an island, he will be returned to land. If he drowns while on the open sea however, he will appear on board the King of Red Lions near the closest island.
The Oxygen Gauge appears as a blue meter below Link's Heart Containers, similar to the Lantern Oil meter. The gauge appears while Link is underwater with the Iron Boots equipped, unless he is wearing the Zora Armor. Unlike previous games, bottled fairies are unable to revive Link if he drowns.
The Oxygen Gauge appears as a circular meter almost identical to the Stamina Gauge, the only difference being color. It appears when Link swims underwater with the Water Dragon's Scale. Using the spin maneuver causes the gauge to deplete faster, and in Hero Mode, it consumes twice as much air. Touching a normal bubble will replenish the meter, while touching a poison gas bubble depletes the gauge. Like previous games, Link's Oxygen Gauge will refill whenever he surfaces. Unlike previous games, when the gauge is fully depleted, Link does not drown instantly; instead, he begins to lose hearts. However if he loses all his hearts after his Oxygen Gauge is depleted while carrying a Bottled Fairy, Link will recover up to six Hearts and his Oxygen Gauge will refill completely. The rate at which the Oxygen Gauge depletes can be temporarily slowed by consuming an Air Potion, and is temporarily stopped completely by drinking and Air Potion+. Also if the Oxygen Gauge is depleted while Link is under the effects of Guardian Potion+ (which temporarily prevents Link from losing hearts) he will not lose any hearts while underwater, can perform infinite spin maneuvers, and can remain underwater until the Guardian Potion+ wears off, at which point he will start to lose hearts. When Link runs out of oxygen, he will swim more frantically and will show obvious signs of distress (regardless of whether he is losing hearts or not).