noun
Refers to a body of water partially enclosed by land, smaller than a sea. The term is somewhat literary or geographical.
入り海の静かな水面に小舟が浮かんでいた。
A small boat was floating on the calm surface of the inlet.
Compound of 入り (iri, 'entering') + 海 (umi, 'sea'), literally 'sea that enters' or 'inlet sea'. The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning.