We were happy to help!
I wanted to comment that each cruise ship is constructed of of different materials and so we have seen many varying results. Most recently we had a Mesh beta tester who used goTenna Mesh on one of the world’s largest cruise ships called the Explorer of the Seas (https://en.wikipedia.org/wiki/MS_Explorer_of_the_Seas).
He was able to reliably communicate with his kids inside a theater on Deck 3, from a restaurant on Deck 14. (See diagram below.)
That being said, there’s no telling how it’ll do on another ship – laws of physics will dictate that but here are some tips. If you’re not getting the range you want, first try having both units outside of rooms/cabins (i.e, go out on deck) to ensure maximum range possible is attained. A second option might be to hide Mesh units as relay nodes in strategic locations on the ship. 
It’s important to remember that each ship is constructed of different materials so your results may vary. But of course you should be able to use them when you dock on-shore too!
Send us photos! Have a great vacation.