eSIM for a cruise itinerary

No. A travel eSIM connects to mobile networks that stand on land. Once the ship passes the reach of coastal masts, the phone has no service. What remains is the satellite Wi-Fi or the cellular service the ship sells, which are separate systems billed separately from your eSIM.

Count the port days you actually intend to go ashore, not the nights on the booking. That said, if the plan's validity runs as one continuous window from activation, you may still need it to stretch from the first call to the last. How validity is counted differs by supplier, so read the plan details before buying.

Not necessarily. If a regional plan names every country on your itinerary, one profile covers the lot. If a call is missing from that list, you choose between adding a country plan for it or accepting being offline there when the stop is only a few hours. What matters is the country list on the plan page, not a regional name that sounds inclusive.

Usually one of a few things: the phone is still holding the old network and has not searched again, mobile data is still routed to the home SIM, or the plan has not been started the way the supplier requires. Cycle aeroplane mode once, check that data points at the right profile, and give it a moment before concluding it has failed.

Turn data roaming off on the home SIM before the ship sails, and if you want to be certain, disable that SIM entirely while at sea — the phone can attach to the onboard cellular system by itself. Charges in that case go to your home operator, not to the eSIM you bought, and only they can tell you the rate.

Not on the eSIM's number — a data-only plan has no number that accepts ordinary calls. They can reach you through a messaging app whenever you are online. Send them the itinerary in advance so they know which days you can reply, and give the cruise line its own onboard contact channel for anything urgent.