There are three main beaches, on the northwest, north, and northeast shores. The north and northwest beaches are on the border of reefs. The depression at the island's center is thought to be a raised lagoon. There is only one known source of drinking water on the island: a brackish spring on the north shore exposed at half tide, rising from a crevice in flat rock, large surfaces of which compose the face of the beach. The surrounding ocean tidal range is about one meter at spring tide.