Unlike open-water diving, where a diver in distress can simply head to the surface, cave diving is a type of penetration diving. To leave the dive zone, the diver must swim back out of the cave, as far as he or she has already penetrated, reversing an often difficult navigational process and requiring enough air to reach the surface. Caves can have strong currents, both of inflow and outflow varieties, and some cave systems have inflows to one egress and outflows from others, meaning that a diver can easily underestimate the amount of time it will take to retrace a route. Visibility can vary wildly from perfect to zero within the same cave. In addition, there is a possibility of getting lost in a cave of any significant size.
All of these factors mean that cave diving is out of reach of casual divers (or should be), and cave exploration thus left to a relatively small cadre of extremely well-trained divers. However, the development of inexpensive and easy-to-use ROVs has changed the balance in cave exploration. ROVs can be sent into the water by people with zero dive experience to explore caverns, caves and cave systems in perfect safety. Modern ROVs have high-resolution video camera systems and powerful lighting systems which permit incredibly detailed views of the underwater environment, efficient electric motors that allow hours of underwater time, and long tethers which permit explorers to penetrate hundreds of meters into underwater cave systems. In addition, a small ROV can be packed overland to inaccessible inland underwater caves, such as the deep cenotes in the Yucatan, or easily deployed from a small boat in coastal locations.
ROVs are also a useful support tool for experienced divers who are exploring difficult or unknown cave systems.
ROVs can be used to ‘scout’ unfamiliar passages or to check whether there is a passageway between two tunnel systems, without putting a human diver at risk. Because ROVs have a much longer dive duration than a human diver, a single scouting mission with an ROV can open up large areas of new caves for the human divers to follow up on. ROVs can also find the most interesting areas for human divers to explore, allowing the limited human dive times to be spent in the most enjoyable or most important areas of the cave system.
Although many underwater cave explorers are motivated purely by recreation or the challenge, there is also considerable scientific interest in exploring underwater caves. ROVs have been an enormous asset to scientists and archaeologists in exploring the cenotes of the Yucatan Peninsula in Central America. Cenotes are large sinkholes that open onto groundwater from an underlying aquifer. There are thought to be more than 2,500 cenotes in the Yucatan area alone, and many of them are of great archeological significance because they were used as ceremonial sites by the Maya civilization. Although many large cenotes have been at least somewhat explored by archeologists in the last century, many remain untouched or even undiscovered. Researchers and explorers have been using ROVs since the early 2000s to explore and map the Yucatan cenotes, as well as the extensive underground cave systems that many cenotes connect to.
As in most areas where ROVs are deployed, ROVs used in cave exploration serve to greatly extend the range and effectiveness of human divers, and also open up new possibilities that simply would not exist without these useful tools.