Does our usual roaming allowance cover a phone connection on the ferry?

The ferry has barely left the mainland when Amélie gets a message mentioning a maritime network. She reaches for the mobile-data switch. Her brother Luc says, “We're going to Corsica. We're still in France.”

Her French mobile plan includes an allowance she normally uses around Europe. Luc wants her to keep a hotspot running so he can finish downloading a film. She is happy to share data on land, but has not checked what the plan says about connections at sea. Neither knows the maritime rate.

There is no bill to dispute yet. The phone has given them a reason to pause before carrying on. Luc thinks they should finish the download first because it is nearly done; Amélie would rather ask what network and tariff they are using before agreeing to share it.

What should they establish now, and how can she stop the hotspot without turning a simple cost question into an argument about whether she is being generous?