During the period when a near-coasted voyage using the geonavigation called 'Jinori' was the mainstream, people had to wait for the changing tide at Tomonoura to sail across the Seto Inland Sea off the Numakuma Peninsula.
「地乗り」と呼ばれる陸地を目印とした沿岸航海が主流の時代に、沼隈半島沖の瀬戸内海を横断するには鞆の浦で潮流が変わるのを待たなければならなかった。