Riko-Riko cave is a large cavern opening from a much smaller entrance with a depth at the opening of about 100 feet and 60 feet throughout. Stories have it that in World War II the Japanese operated submarines from within the cavern in preparation for an invasion. Because of the surrounding depths, Riko-Riko cave offers one of two safe anchorages in the Poor Knights. The other anchorage at South harbor is open to the southern weather, whereas Riko-Riko cave faces North-west and offers a calm anchorage under most weather conditions. It also offers a marvelous site for a night dive. After the night dive you can try catching flying fish attracted to the lights of the boat. They make a good breakfast the next day.