I used the air bladder early on which is kind of fun while you don't have good O2 tanks or vehicles yet. That way you can zoom to the surface with that air balloon. Unfortunately I don't find it useful anymore once you get some of the other gear. It also would have been kind of cool if they had a diver weight belt system to do the opposite. With your O2 full, be able to quickly fall like a rock to the bottom of where you want to explore with relatively full O2, giving you back the wasted time it takes to swim to the bottom, then drop belt and deploy your airbag when its time to go back up for air.
I saw that bit of kit, wasn't sure if I wanted to have it, but I can see the usefulness on a deep dive. I'm going to be doing some more deeper exploring very soon, I may bring one along just to see how it works.
Elite Dangerous: CMDR JohnnyChemo MWO: Johnny Keemo
Always be yourself. Unless you can be Batman. Then always be Batman.