The Air Bladder is a day-one craftable safety tool. It provides an emergency rapid ascent toward the surface when you have misjudged a dive or are fleeing a predator.
New for the sequel’s 4-player co-op, it can also share a few seconds of oxygen with nearby divers — a small but meaningful cooperative mechanic that turns a personal safety device into a way to rescue a teammate who is out of air far from the surface.