What is the minimum number of depth and timing devices required for a safe cave dive?

For a safe cave dive, it is essential to have a redundancy in critical equipment to ensure that divers can monitor their depth and time accurately. The minimum requirement of two depth and timing devices is significant because if one device fails, the diver can rely on the other to assess their situation accurately. This redundancy is a crucial aspect of safety, particularly in cave diving, where environmental factors can complicate visibility and orientation. Having only one device creates a single point of failure, which can lead to potentially dangerous situations if that device malfunctions. Therefore, utilizing two devices enhances safety management and contributes to overall dive planning and execution, which is paramount in the technical environment of cavern diving.