What should a diver do if their primary light fails during a night dive?

Staying calm and using backup lights is the appropriate response if a primary light fails during a night dive. This action is crucial because panic can lead to poor decision-making, increasing the risk of disorientation or accidents in the dark underwater environment. Backup lights are a key part of night diving equipment, and having them ready ensures that divers can maintain their visibility, navigate, and communicate effectively with their buddies.

The other options may seem reasonable under different circumstances but do not address the immediate need for light. Surfacing immediately may expose the diver to hazards on the surface or lead to a disconnection from their dive team. Signaling for help could be impractical without a light source to signal effectively, and attempting to fix the light underwater could potentially be unsafe and unproductive in low visibility conditions. Therefore, relying on backup lights while maintaining composure is the best course of action to ensure safety.