Upvote:3
Since ships, as do airlines, document passengers with a manifest, your absence may be noted, but little else. They will know quite a bit about you as your reservation includes all your identifying information (name, date of birth, contact phone and email) and you present your passport/identity document in order to board.
As a cruise ticket is based on a round trip, you may want to check the fare conditions, to ensure that you would not be charged the higher one-way fare in the event you fail to appear for the return leg.