When I first looked into this, I assumed my eSIM would somehow be using the ship’s own WiFi. It isn’t — and once you understand what’s actually going on, the whole thing makes a lot more sense.
Ship WiFi and cellular at sea are two completely different systems
The WiFi package the cruise line sells you — the one that needs a login and a password — is the ship’s own internet, usually beamed down via satellite. It’s separate from everything else here, and it’s not what your eSIM uses.
What your eSIM is actually connecting to
Big ships have small mobile phone transmitters fitted on board — sometimes called picocells — installed by specialist maritime providers. These create a tiny mobile network that floats around with the ship, linked back to land via the ship’s satellite connection. A few miles offshore, your phone picks this up as an actual mobile signal, not WiFi — you might even see a network name like “Cellular at Sea” appear.
Why you need a proper eSIM plan for this, not just roaming
Here’s the bit that catches people out: if your ordinary phone contract just roams onto that network by itself, the price can be eye-watering — that’s where those shock roaming bills come from. A GigSky or Maya eSIM works because it’s set up in advance with an affordable rate for that same onboard network, instead of your home provider’s emergency roaming price.
And once you’re in port?
Once you’re close enough to shore — roughly 12 nautical miles — your eSIM just switches over to the country’s normal local mobile networks, exactly like on any regular trip abroad.
So no — you’re not piggybacking on the ship’s WiFi. You’re piggybacking on the ship’s own private mobile network, and a proper eSIM plan is what makes using it affordable instead of a nasty surprise on your next bill.