Tanks full of normal air don't last long as breathing devices, but a large air tank is excellent for ensuring a character has a swiftly rising buoyancy, and a savvy diver can adjust her air tank just enough to give her a neutral buoyancy, making it much easier to explore underwater. Every 6 gallons of air is enough to breathe for roughly 1 minute underwater; it takes far less air for a Medium creature to achieve neutral buoyancy unless it's carrying a significant amount of metal and other dense material.
- Aquatic Adventures
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