Cave diving is a combination of underwater diving with the added bonus of doing it in caves that are at least partially filled with water. The equipment used varies, but is typically scuba equipment with specialized configurations. Cave diving is highly technical as it can involve small squeezes similar to that of regular caving above water, but it’s done at depths that will require decompression.
Because cave diving is a form of penetration diving, in an emergency a diver cannot swim vertically to the surface but must swim the entire way back out. The sport can require underwater navigation through cave systems which may be difficult, and additionally have exit routes that are a considerable distance, which would require the diver to have sufficient scuba tank gas to make the journey back out.