Stage bottle (deco / bailout gas)

A stage bottle is an extra tank you carry on your side. It provides a secondary gas supply if your main regulator fails. Divers use these cylinders for decompression stops or as bailout gas during deep technical dives. You will often see divers in Koh Tao using small 7-liter steel tanks for deco, while Komodo tech divers might carry larger 12-liter aluminum bottles. These tanks add significant weight and drag to your profile.

Always check your gas math before you descend. I once saw a diver in Cebu forget to account for the 50 bar reserve needed for his stage bottle. This mistake nearly caused a panic when his primary supply ran low. Ensure your manifold or regulator is securely mounted because a loose bottle can strike your legs during a descent. Keep your hoses tidy to prevent entanglement.