Hurricane Iniki struck Kauai in September 1992 and again caused extensive reef damage along the south and west shores. Presumably the reefs of neighboring Niihau experienced similar destruction. Niihau does not have any substantial bays that could shelter coral development. The island is of insufficient size to protect portions of its coastline from wave refraction effects. Extreme northwest swell frequently impacts the north and western shores of Niihau during the northern hemisphere winter.
South swell impacts the southern coast during the northern hemisphere summer.
Pinnacles, overhangs, underwater caves and vertical walls exist along the northwest shoreline and biologically rich reef communities are said to occur off the south end of the island. However, little scientific information is available. Where corals are found, they reportedly exist as thin veneers on limestone and basalt outcrops. The Robinson family has privately owned the island since 1864. The island is operated as a cattle ranch.