Sharks Cove is a popular snorkeling and diving site on the North Shore of Oahu. Sharks Cove was the first area that Chrissy and I began looking for caves, having heard rumors of lava tubes in the area. We were quite surprised to find that there are actually zero lava tubes in the area, but there is a 20 to 30 foot thick bed of calcified beach sands that has been both chemically and mechanically eroded to create a significant number of small caves. Within 6 months, we had mapped more than a mile of passage. Local dive operations run hundreds of new and visiting divers through the area daily both weekends and during the week, none of which observe any sort of safety with regards to overhead environments. Diving in the “swimthroughs” is a popular destination dive. For the most part, many of the caves are less than 50 feet from open water, but a few caves have significant sidemount or no mount restrictions that lead to more extensive passage.
As expected, there have been fatalities in the caves here, the worst being a triple death in one of the more complex caves in the area. Three marines died in a cave called Death Cave, at a feature called the Elevator Shaft. on 3 July, 1987 they entered at the Elevator Shaft, a hole in the top of the limestone bed that leads to the rest of the cave. Instead of exiting the cave into the ocean, less than 200 feet away, they got lost in the multiple tunnels leading from the Elevator shaft into the limestone bed. Each diver was new, the most experienced open water certified for two years, the other two divers, for two months. They were not equipped for cave diving, having only one tank and regulator each, and an unknown quantity of lights.