Ariake Sea
The is a body of salt water surrounded by Fukuoka, Saga, Nagasaki, and Kumamoto Prefectures, all of which lie on the island of Kyūshū in Japan. It is the largest bay in Kyūshū. Its deepest point is only about 50 meters (165 ft) deep, and extreme tides exceed , covering roughly . Isahaya Bay is a branch of the Ariake Sea. Across the Amakusa Islands lies the Yatsushiro Sea.