In port and close to shore, yes — that is ordinary land coverage. Out at sea or in the air, no, and that is a protection rather than a limitation
On a Cruise
Works
- Alongside in port
- Anywhere within reach of a coastal mast, which is often several miles out
- Every shore excursion, provided the country is on your plan
Does Not Work
- Open sea, beyond land coverage
- The ship's own onboard mobile network
The ship's onboard network is the expensive one. It is a satellite service with its own operator name, and a phone connecting to it roams at maritime rates — among the highest charges in mobile telephony, and billed by your home operator. A travel eSIM will not connect to it, which is exactly what you want. Keep data roaming off for your home SIM for the entire voyage.
A Regional Plan usually suits a cruise better than a Country Plan, because the itinerary is several countries by definition. Pick the region the ports are in, not the one the ship sailed from.
On a Plane
Nothing mobile works in the air, for anyone. Aircraft require flight mode, and where inflight connectivity exists it is the airline's own Wi-Fi, bought from the airline and unrelated to any SIM. A travel eSIM neither helps nor hinders — connect to the aircraft's Wi-Fi as you would in a café.
Install your eSIM before boarding rather than in the air. Installation needs an internet connection, and aircraft Wi-Fi is not always reliable enough for it — see Do I Need an Internet Connection to Install My eSIM?
