What came to mind was be one of the complete CDs from Music2Hues. I happened to do a search on the website using "tropical" and came up with these:
http://www.music2hues.com/cart/flag/2_I ... opical.htmAfter doing a quick survey of the list, the last collection (Trade WindsCategory) seemed to have some nice pieces. Though since I don't have a feel for what your show looks like, maybe one of the others listed on that page would do as well.
Some additional thoughts....
Since the Yacht company benefits from having a nice show advertising their service, the least they could do is to pay for the music used in the show so the show has good legit Royalty Free music that fits the production. It's still a great bargain for them. Even a non-profit organization was happy to pay for the music for a show I made for them a few years ago so they could use the show without worrying about copyright infringement in their presentations etc.
So rather than going in the hole and forking over the money for the music from your pocket, offering them a copy of the show for ability to use on FB and YT for the price of the music will run about $45. You maintain the royalty free music license (for the whole set) when you buy it and can use the music in other projects too. (Review the terms of use before purchase to be sure it fits your needs ). Draw up a simple agreement that states the show price and what they can use the show for and you may be good to go music wise.