I'm retired with tangible assets and land in quasi rural Australia .. so this is largely moot to me, however ...

What of those interested in retiring to a cruise | floating accomadation ship?

That's a serious question for some, I saw a thing the other night and caught an elderly well off couple saying they looked at many options and shipboard life was cheaper and more interesting (personal opinion) than other assisted living retirement options.

Raises the question of a digital life on international waters > 9 months of the year.

In the US the 'Saverin' rule defines that you are a US citizen regardless of where you are domiciled. You pay federal tax with certain caveats. State tax may also be collected unless you cut ties ....

Wondering if we need to add 'International Waters' to the retirement location dropdown.......!