Ivilla I-River Sea iyivilla esesiqhingini i-Awaji Island esifundazweni i-Hyogo, e-Japan. Le ndawo isondelene nomlomo womfula, futhi umgudu wohlelo lokwakha usuka enyakatho uya eningizimu ubheke emanzini. Isakhiwo sihlukaniswe saba yizingxenye ezintathu: isakhiwo sokungena, isakhiwo sezivakashi kanye nesakhiwo esiyinhloko. Amagceke amabili ahlukanisa lezi zingxenye ezintathu, futhi umgwaqana uyazixhumanisa. Eduze komgwaqana, umngcele phakathi kwangaphakathi nangaphandle uba nobumnene. Izindonga zimbozwe ngamathayela emingcele enziwe ngamathayela ophahla endawo yase-Awaji. Isitezi esisodwa sikhawulela umthelela ezindaweni ezizungezile.