What action is recommended if a primary light fails during a dive?

When a primary light fails during a dive, deploying a backup light is the recommended action. Backup lights are an essential part of cavern diving equipment as they provide divers with an immediate alternative source of illumination, which is crucial in dark environments like caves where visibility can diminish quickly.

Having a backup light ensures that divers can safely navigate and communicate with each other while maintaining spatial awareness of their surroundings. This action helps prevent disorientation and potential accidents in low-light situations.

In cavern diving, the importance of light cannot be overstated; without it, divers lose vital visual references that are crucial for safe navigation. Therefore, relying on a backup light allows divers to manage the situation effectively without compromising safety.