 FACT: First off most Cave divers do not use wetsuits, they use  drysuits. Secondly underwater caver explorers never move into  unexplored territory without running a navigation line so they can  find a way back or out. Several scenes show the explorers using  their HID (High Intensity discharge) dive lights out of the water.  HID lights use the surrounding water as a coolant and thus cannot be  used for long periods of time above water as they would heat up too  much and croak.