If a diver becomes unconscious or incoherent at depth, what should the buddy do first?

• A. Add O2 to the diver's UBA
• B. Abort the dive immediately
• C. Switch the mouthpiece to surface position
• D. Return to the surface without aid

Answer: (A)

Providing oxygen to the diver’s UBA is the first action because the immediate danger is hypoxia. When someone becomes unconscious at depth, their brain and vital organs can suffer quickly if oxygen delivery isn’t restored. Adding O2 to the diver’s UBA ensures they continue to receive oxygen right away while you manage the rescue and plan the ascent.

Aborting the dive immediately or returning to the surface without aid would leave the diver without targeted oxygen support during an at-depth emergency, which can worsen the outcome. Switching the mouthpiece to surface position would cut off the available oxygen supply at a critical moment. The priority is to stabilize oxygen delivery first, then proceed with safe ascent and further care as needed.