Rebreather

"A disposable chemical scrubber that can extract oxygen from water during brief submerged operations."

- Deus Ex description

A rebreather is an item that allows its user to breathe while underwater. In Deus Ex, rebreathers give the player a full breath meter as long as the item lasts. Rebreathers can be used to great effect in Hong Kong and the MJ12 Ocean Lab, but elsewhere it isn't worth carrying around.