Cruisers have such tight budgets I doubt if they would pay much.
Maybe a three level process.
1) Postcard size with photographers details. To hook 'em in right away. Free!
2) A4 size digital prints/YouTube quality video, for the files, photographers name on back. Say $20 a go.
3) Full set of files on disk including all
copyright. For when they're back, the boats been
sold and only memories remain. Whatever the market will bear.
Sort of like wedding photos.