We have been doing cruises for about 10 years now, and when Geocaching reared it's ugly head it was a must to pack the GPS & PDA full of downloads! The problem I have found was pinpointing the areas for the downloads. The Caribbean wasn't too bad I just had to pinpoint an imaginary point somewhere in the Sea and request caches on a radius of 400 or so miles that would include all the Islands we would be visiting (there all in a semicircle) you may have to filter out 3 or more stars to give you 500 caches.
The Med & Red Sea are a bit more difficult, most of the caches are where you visit on your tours -- remote from the docks & even though the tour bus takes you to walking distance you haven't got the memory on the PDA to get every possibility, the times Ive kicked myself on returning home & checked out Google Earth!!
The Cache on a route system looks good. A similar Cache on a Cruise would be brilliant
Keep on Cruisin & Keep on cachin!
