Turnaround day, the afternoon between two ships
A turnaround day is the day one voyage ends and another begins: the cabin gone by breakfast, the next room not ready, and an afternoon in between.
Couples doing back to back voyages, or ending one sailing and starting another a day later, run into the same shape every time. The cabin has to be empty by early morning. The next room, wherever it is, will not be ready until the middle of the afternoon. What sits between them is several hours with no door to close.
Where the gap opens
Usually between ten in the morning and three in the afternoon, occasionally wider. It is not free time in any restful sense, because the two of you are carrying a day bag and watching a clock, and the city is being visited rather than enjoyed.
What can be booked into it
A day room, which is an ordinary hotel room taken for part of a day and treated by the house exactly like any other address. Once a room number exists, an hour can be arranged into it on the usual forty to sixty minutes. One hour, made dense rather than long, is the format that fits an afternoon with a boarding time behind it.
What should not be booked into it
Anything that finishes close to a boarding window. A three hour session on a turnaround afternoon is a way of arriving at a gangway in a hurry, which undoes the point of the booking. The page on turnaround days works through the timing in detail.
Luggage, on the day it matters most
Large cases usually go into a luggage room or forward with the line, and what stays with the two of you is one bag each. That is the version of the day that works. Carrying everything around until three is the version that does not.