A seafarer is never at the front or the back of a ship; they are at the bow or the stern. They are never on the left or right side, but rather port or starboard. They are never in their bedroom or the kitchen, but they might be in their cabin or in the galley. A ship’s speed is not measured in miles or kilometres per hour, but rather in knots. A ship, of course, is referred often as “she” and not always as “it”.
These are the things we might think of when we hear a phrase like “Maritime English”.