If a diver has completed a previous oxygen dive, what defines a successive oxygen dive?

A successive oxygen dive is defined by the context of the intervals between dives and the use of oxygen as a breathing gas. Specifically, this concept emphasizes the importance of the Off-Oxygen Interval, which is the time spent breathing normal atmospheric air after using pure oxygen during a dive.

In this case, option B is correct because it highlights the condition of having an Off-Oxygen Interval of less than 2 hours following a previous oxygen dive. This shorter interval represents a state where the body's tissues may still have a residual saturation of oxygen, increasing the risk of central nervous system oxygen toxicity and other dive-related complications. Therefore, understanding the time restrictions is crucial for safe diving practices.

The other options do not correctly describe what constitutes a successive oxygen dive. For instance, a long surface interval or depth greater than 30 fsw does not inherently define the conditions for a successive dive in terms of safety and physiological factors associated with oxygen use. Additionally, the partnership of a diver does not influence whether a dive is classified as successive in this context. Hence, option B accurately captures the critical criteria for defining a successive oxygen dive.