Seto Inland Sea is not a true inland sea, being neither an epeiric body of water like Hudson Bay nor an isolated endorheic basin like the Caspian Sea. Rather, it is actually a marginal sea: a division of a wider ocean (in this case the Pacific) which is partially enclosed by islands, archipelagos, or peninsulas (here, the Japanese Home Islands), adjacent to or widely open to the open ocean at the surface. The Naruto Strait connects the eastern part of the Seto Inland Sea to the Kii Channel, which in turn connects to the Pacific. The western part of the Seto Inland Sea connects to the Sea of Japan through the Kanmon Straits and to the Pacific through the Bungo Channel. Each part of the Seto Inland Sea has a separate name in Japanese. For example, refers to the strait between Ehime, Yamaguchi, and Ōita prefectures in the western portion of the sea; is the open expanse west of the Geiyo Islands, near Hiroshima prefecture; and refers to the expanse between Yamaguchi prefecture and Suō-Ōshima. These areas are sometimes styled Iyonada, Akinada, and Suonada. There are also many straits located between the major islands, as well as a number of smaller ones that pass between islands or connect the Seto Inland Sea to other seas or the Pacific. Almost 3,000 islands are located in the Seto Inland Sea. The largest island is Awaji-shima, and the second largest is Shōdo-shima. Many of the smaller islands are uninhabited. Major islands Eastern part: Awaji Island, Shōdo Island, Ieshima Islands, Naoshima Islands, Shiwaku Islands, Yumeshima Central part: Ōmishima, Innoshima, Itsukushima (popularly known as Miyajima), Hinase Islands, Kasaoka Islands Western part: Suō-Ōshima, Uwakai Islands, Hashira-jima Islands. Fauna Over 500 marine species are known to live in the Seto Inland Sea. Examples are the ayu, an amphidromous fish, horseshoe crab, finless porpoise, and great white shark, which has occasionally attacked people in the Seto Inland Sea. In the past, whales entered the sea to feed or breed, however because of whaling and pollution, they are rarely seen. History During the last ice age the sea level was lower than today. After the ice age, sea water poured into a basin between the Chūgoku mountains and Shikoku mountains and formed the Seto Inland Sea as it is known today. From ancient times, the Seto Inland Sea served as a main transport line between its coastal areas, including