 Only those who have valid cave diving certificates are permitted to enter, requiring a staff member to unlock the gate, and typically accompany them during the dive.In 2010, Ben McDaniel, a diver who was not certified for cave diving, but had been witnessed by staff and other divers gaining access to the restricted area of the cave by forcing open the gate, did not resurface after an employee let him through the gate one evening.It was initially assumed that he had died accidentally after becoming trapped underwater, but extensive searches did not find his body, nor any sign that one was present in the remote recesses of the cave.