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 MJ-12 Ocean Lab, but elsewhere it isn't worth carrying around.