Talk:Standard O₂ Tank/@comment-26921554-20160625125025/@comment-124.190.72.80-20161213114142

Just for trivia sake, a lot of movies you've seen where they're running a complicated two tank setup, its actually a rebreather. Instead of venting the used oxygen to the outside it sends it through the system to be reused. The second tank contains an agent used for this process. You can't go as deep with them due to the complexity of the build but they're generally noiseless to the outside and have "longer range".

As to the poster talking about a second tank messing with your weight, compensating for the tanks weight by taking stones off your dive belt fixes this.