Jiazi Yichou Haizhong Jin (甲子乙丑海中金) refers to the concept where Zi (子) belongs to water, representing both a lake and a place where water is abundant. Additionally, metal perishes in Zi (子) and is buried in Chou (丑). With water being abundant and metal perishing and being buried, it is thus called Haizhong Jin (海中金), or "Gold in the Sea."