noun
lagoon; coastal lake
A lake formed when a bay or inlet is cut off from the sea by sediment deposition or coastal uplift. Used in geography and earth science contexts.
サロマ湖は北海道にある海跡湖です。
Lake Saroma is a lagoon in Hokkaido.
ラグーン is a loanword from English, often used in tourism or casual contexts, whereas 海跡湖 is a technical geographical term.
Compound of 海 (sea), 跡 (trace/remains), and 湖 (lake), literally 'sea-remnant lake'. The term is a modern geographical coinage.