noun
offshore breakwater
Technical term in coastal engineering for a breakwater built away from the shore to reduce wave energy.
この海岸には離岸堤が設置されている。
An offshore breakwater has been installed along this coast.
Compound of 離岸 (rigan, 'offshore') and 堤 (tei, 'embankment, bank'). The exact historical derivation is uncertain, but the term is a modern technical coinage.