noun which may take the genitive case particle 'no'
freshwater; limnetic
Used attributively to describe organisms or products originating from freshwater environments. Often appears in scientific or commercial contexts.
Many freshwater fish inhabit this lake.
Freshwater pearls are often cheaper than saltwater ones.
海水産 means 'saltwater/marine (product/organism)', the counterpart to 淡水産.
Formed from 淡水 “fresh water” and 産 “originating or produced in,” hence “of freshwater origin” or “living in freshwater.”