1TTW in or under the sea and not far from the coast [↪ inshore, onshore]:
offshore oil fields
an offshore island
offshore oil fields
an offshore island2PETBF banks etc that are based abroad in a country where you pay less tax than in your home country :
offshore financial centres
offshore banks/companies/investments etc
offshore financial centres —offshore adverb:
a boat anchored offshore
a boat anchored offshore