I am going on cruise to the carribean on norwegian gem- what should I do to be ale to get data for emails and text?

Thank you very much, Drew, for your detailed response above.

My husband and I are currently on a Scandinavian cruse, so we bought the $50 International plan, but we can’t seem to get any definite information on the T-Mobile website that answers the following questions:

Does it apply to both our phones or just one?

If just one, how do we select the one phone?

Does it apply on the ship when we're at sea?  It sounds like you're saying we may not be able to text or use our phones to surf the net or read or send emails without an exorbitant charge.  Where on their not very helpful website would we find the official answer to these questions?

Thank you very much!