What should a diver do in an out-of-air emergency?

In an out-of-air emergency, the diver should activate the backup air supply or ascend while signaling for help. This response is vital because initiating the backup air supply provides an immediate solution to the critical situation. It ensures the diver has access to air, reducing the risk of losing consciousness or experiencing a blackout due to hypoxia.

Additionally, ascending while signaling for help is crucial for the diver's safety. This action alerts any nearby divers or support personnel to the emergency, enabling them to provide assistance if needed. Ascending helps to manage the urgency of the situation since reaching the surface can be a more controlled environment for resolving the issue, assuming proper ascent protocols are followed to avoid decompression sickness.

Overall, this response is a critical safety procedure that aligns with training and emergency protocols for divers, ensuring the best possible outcome during an out-of-air emergency.