The first night ashore, after the ship
The night a voyage ends is the one night of a cruise trip with nothing behind it, which makes it the night the longer formats belong to.
A couple who has just left a ship is in an unusual state and rarely notices it. The body has spent days compensating for a floor that moved and keeps compensating for a day or two after the floor stops. Sleep has been arranged around somebody else’s timetable. There has been no privacy that did not have a corridor attached to it.
Why the diary is the point
Whatever else is true of this night, nothing is printed on it. No boarding hour, no transfer, no muster. A flight home may sit a day or two later, which is a different kind of pressure and a much gentler one. That emptiness is what makes the night worth booking properly rather than booking short.
What suits it
Length. Three hours, or the eight hour block, or two therapists, all of which sit badly on an embarkation evening and sit naturally here. The page on the evening after a cruise explains the choice, and the guide on a first night back on land takes it further.
Sea legs, in practice
Standing still can feel like moving for a day or so afterwards. It settles on its own. It is worth mentioning in the thread only because it changes what the two of you will want, not because anything about the booking changes.
Book it before you sail
Shipboard internet is unreliable and expensive, and the last morning of a voyage is a poor time to be writing a first message. Arrange this night at the same time as the embarkation one, months earlier if you like, and leave one free move of the date in reserve.