What should a diver do first if they experience an air loss?

When a diver experiences an air loss, the first step should be to check the main tank valve. This action allows the diver to quickly assess whether the situation can be resolved by simply turning the valve back on, which might resolve the air loss issue without needing further intervention. Understanding the equipment and verifying that it is functioning properly is crucial in a high-stress situation like air loss underwater.

Successfully checking and securing the main tank valve can provide the diver with immediate air access, and would enable them to reassess their situation and determine the next steps, such as switching to a backup regulator or notifying the support team, if necessary. On the other hand, immediately switching to a backup regulator or performing an emergency ascent without first checking the main tank could lead to unnecessary complications or risks in a potentially dangerous situation. Therefore, ensuring the main tank valve is operational is the foundational step in effectively managing air loss while diving.