The art of doing nothing at twenty knots

Look at almost any long cruise itinerary and the sea days sit between the ports like punctuation nobody quite trusts: smaller type, fewer words, occasionally missing entirely from the marketing photograph. This is the wrong way round. A sea day is not a gap in the holiday. On a genuinely long voyage, it is frequently the majority of it, and treating that time as dead weight rather than the point is a good way to have a worse cruise than the one you paid for.

Why the longer voyages need them

Distance is the honest explanation. A crossing of the Atlantic, of the kind that leaves London Tilbury bound for the Caribbean by way of the Azores, simply requires several consecutive days at sea, because there is no island conveniently placed to break the passage up. The same logic applies at far greater extremes on a voyage that runs from Southampton down through the Atlantic, along the Amazon and on to Antarctica: eighty-odd nights that include long stretches with no coastline in sight at all, because the places being connected are, by any ordinary measure, a very long way apart.

A shorter Caribbean crossing makes the same point on a smaller scale. Between the Azores and the first landfall in the Caribbean lies open Atlantic with nothing to see for the best part of a week, and a passenger who has booked the trip purely for the islands at either end is, in effect, spending several days waiting for the holiday to properly start. The better approach is to treat the crossing itself as part of what was booked, rather than the price paid to reach it.

What the ship actually offers

A ship at sea is, in effect, a small town that has to entertain itself without any help from the destination. Most carry a library, and it is generally underused relative to how good libraries at sea tend to be; a lecture programme, when one is offered, is often the most interesting hour of the day, covering the history or wildlife of wherever the ship is headed; and the deck itself, with nothing but ocean in every direction, has a way of resetting a traveller's sense of scale that no itinerary photograph quite captures. A sailing north past the Faroes towards Iceland, watching for the seabirds and occasional whales that follow a ship's wake in these waters, turns the sea day into the wildlife-watching opportunity, rather than the interruption to it.

The rhythm worth settling into

The people who enjoy sea days most tend to be the ones who stop treating them as time to be filled and start treating them as time with nowhere in particular to be. Breakfast without an excursion to catch, a book finished rather than merely started, a conversation at dinner that runs long because there is no early start the next morning. It takes most first-time cruisers a day or two to stop reaching for their phone to check what time the coach leaves, and rather longer to admit how much they were enjoying not knowing.

What to actually pack for one

The practical advice is simple and often ignored. Bring more to read than you think you will need, because a good sea day has a way of consuming a book faster than expected. Bring binoculars if wildlife of any kind is even a passing interest, since dolphins, seabirds and, in the right waters, whales appear with more regularity on open water than most passengers assume. And resist the temptation to book every lecture and quiz on the daily programme; the best sea days generally have at least a few hours left deliberately unplanned.

None of this requires a particularly long cruise to matter. Even a modest sailing to Iceland includes at least a day or two of open water on the way north, and passengers who arrive expecting only the ports tend to find those days the most restful part of the trip once they stop waiting for them to end. The sea, it turns out, does not need an itinerary of its own to be worth the time spent looking at it.