Located near Diamond Head, 100 Foot Hole is an ancient Hawaiian fishing ground that was accessible only to the Ali'i (Royalty). Although this hole is only 70-90 feet deep, it got its name from fishermen, who, after being asked how deep it was, answered, "it's about a hundred feet" and the name has stuck. The site is constructed from a cluster of volcanic rocks tumbled together to form ledges, caves and one large open-ended cavern. One formation, encrusted with cauliflower coral, houses the main tunnel. Within that tube there is an obstructing rock that can easily be traversed. Boats tie off to a naturally formed lava anchorage in 75 feet, just south of the focal boat of the dive. Bring a light to view the bountiful marine life inside the cave.