Oxygen

When a player is submerged in water, his or her oxygen level begins to decrease. Once the bar is fully depleted, the player will begin to receive damage. The oxygen bar can protect a player from receiving drowning damage for about 20 seconds. It refills slowly as long as the player's head is above the water's surface.

Before game coins were released, the player's HUD featured an oxygen bar. However, that feature was removed in December of 2014 when the HUD was updated to accommodate a game coin count.