Koko bench, the proposed name for a submarine bench 5 m below mean lower low water, is well exposed on the east side of Hanauma Bay off Oahu, Hawaii. The bench is as much as 12m wide and is bordered by a nearly vertical cliff on the shoreward side and by a marginal rampart as much as 1 m high on the seaward side. The fringing reef in Hanauma Bay has overgrown Koko bench. Carbon-14 dating of cores from the reef at the horizon of Koko bench indicates that the bench formed no more recently than 4,100 to 4,400 yrs B.P. The reef has been growing at the rate of about 30 cm per 50 yrs during the time that the dated portion was accumulating.