Final answer:
In an out-of-air emergency while scuba diving, you should share your air with your buddy and safely ascend together, making all required safety stops to prevent decompression sickness.
Step-by-step explanation:
In an out-of-air emergency, if your buddy is close enough, you should share air from your own supply and ascend together safely. This is paramount for the safety of both divers involved. Ensuring you know pre-dive hand signals and having an agreed-upon plan are critical for dealing with such emergencies efficiently.
Learning and practicing buddy breathing techniques during diving courses is essential to be prepared for any potential underwater emergency. Promptly sharing your alternative air source allows both you and your buddy to ascend slowly, performing any necessary safety stops to prevent decompression sickness. Always remember to stay calm and follow your training.