It's amazing how many businesses cater to ships in big port cities. In Detroit, small boats ply the river providing goods and services to the vessels waiting their turn at the docks or to proceed up or down the river.
The Archdiocese of Detroit has a priest whose main job is to go out to the ships to perform marriages, christenings, hold masses and perform other rites.
There are doctors and nurses who do ship visits.
Many of the ship workers cannot go ashore for various reasons, immigration or legal, so the services must come to them.