What is the maximum depth for a standby SCUBA diver using a fully charged single cylinder with less than 100 SCF air?

For a standby SCUBA diver utilizing a fully charged single cylinder with less than 100 cubic feet (SCF) of air, the maximum operational depth is influenced by dive safety protocols and air consumption rates. A typical rule of thumb for recreational diving suggests that divers can generally operate safely up to depths of around 60 feet of seawater (FSW) when working with such limited air supply.

The rationale behind the choice of this maximum depth stems primarily from the need to ensure that, in an emergency or ascent scenario, the diver maintains sufficient reserves of air for safe ascent and potential surface interval durations. At depths greater than 60 FSW, the air consumption can significantly increase due to the higher pressure and the need for additional air for safe recovery procedures.

Furthermore, this depth aligns with standard practices among diving organizations and safety guidelines which emphasize maintaining conservative limits to promote diver safety, especially when utilizing a single tank of limited capacity. This depth allows for adequate safety margins in case of unexpected situations that might demand a more extensive air reservoir.