What is the least desirable scenario during a night dive regarding lighting?

The least desirable scenario during a night dive regarding lighting is when your primary light fails and you have no secondary light. In night diving, visibility is heavily reliant on artificial light sources due to the absence of natural light. When the primary light fails, it significantly compromises safety as divers are unable to see their surroundings, navigate effectively, or identify potential hazards. The absence of a secondary light means there is no backup option to maintain visibility, which increases the risk of disorientation and accidents underwater.

While having a buddy nearby is important for safety, and factors like depth and water temperature can impact the dive experience, the failure of lighting equipment poses an immediate and critical safety concern that can lead to panic or dangerous situations. Therefore, ensuring that divers have functional, reliable lights, ideally with backups, is key to a safe night diving experience.