The air tank is a loot item found in Stranded Deep. Air tanks can be found in hard cases or lockers contained within shipwrecks. It will grant the user a fresh breath of air whenever used. Air tanks are necessary for when the player explores deeper depths; attempting to dive too deep for too long will result in less time to return to the surface to breathe before drowning. Once an air tank is exhausted of its air supply, it cannot be refilled and must be discarded.
Prior to v0.03, each tank could only be used once before exhaustion. As of v0.03, the air tank can be used a total of five times.
If the player ran out of uses for the air tank, it was still considered usable; this bug has been fixed as of v0.02.
Like other loot items, despite spending a considerable amount of time inside underwater shipwrecks, the air tank manages to remain almost completely well-preserved, to the point where almost none of its supply of air seems to have leaked out by the time the player discovers it.
As of 2/07/16, clicking on an underwater locker, console, toolbox, door, etc seems to consistently lock the action button to the last of those objects toggled, rendering the air tank (and any other item) useless while waterborne.