Does Find My iPhone work on a cruise ship?

Not in any way you can rely on. Find My reports a location by sending it over the internet, and once the ship leaves port there is no internet unless someone has paid for it. What you usually see is where that person last stood in a port, hours or days ago.

Why the offline trick doesn't save you

Find My has a clever feature on land: a phone with no connection of its own can still be spotted by other people's Apple devices passing nearby, and their internet connection carries the sighting back to Apple.

That depends entirely on the strangers around you having a working internet connection. On a cruise ship almost nobody does. So the mechanism that rescues a lost iPhone on a city street has nothing to work with at sea. Android's equivalent works the same way and fails for the same reason.

What does still work

• In port. As soon as phones pick up a local network or wifi, locations update. This is genuinely useful for the "has everyone got back to the ship" question.
• If everyone has bought wifi. With every phone on a paid package and actually connected, Find My behaves roughly as it does at home. The catch is that phones drop the network while they sleep, so a location can be an hour stale without looking stale.
• The cruise line's own app. Several lines show where your party is, using the ship's internal network rather than the internet. Accuracy varies a lot.

What we do instead, and why it is a smaller claim

CruiseLink does not track anybody and does not put anyone on a map. That is deliberate, not a missing feature. What it tells you is when each person was last reached — which is a fact it can actually stand behind, rather than a dot that might be eight hours old.

It also has something built for the specific moment this page is really about. If you cannot find someone, anyone in the group can start a search and every phone in the group joins in. Whichever one reaches them says so. The person being looked for gets an alert with one button, I'm here, which ends the search for everybody at once.

More on finding someone onboard, including what the ship itself will do.

The thing worth doing before you sail

Agree a meeting point and a time, named precisely — "the bar on deck 7 by the atrium", not "the bar", of which there are four. It is unglamorous and it is still the most reliable tool on this page. Write cabin numbers on paper, too. Phones go flat.

Get CruiseLink

Free, no account, nothing to set up beyond your group. On iPhone and Android, and the two work together.