The narrow entrance to the harbour is to the east of the Miramar Peninsula, and contains the dangerous shallows of Barrett Reef, where many ships have been wrecked (notably the inter-island ferry  in 1968). The harbour has three islands: Matiu/Somes Island, Makaro/Ward Island and Mokopuna Island. Only Matiu/Somes Island is large enough for habitation. It has been used as a quarantine station for people and animals, and was an internment camp during World War I and World War II. It is a conservation island, providing refuge for endangered species, much like Kapiti Island farther up the coast. There is access during daylight hours by the Dominion Post Ferry.