Normally, I would say travel medical insurance falls into the gimmick category. But if you’re concerned about it, I would suggest double-checking your current policy through your provider to see exactly what you’ve got and how far it extends in terms of coverage compared to any risk factors you may be facing.
The only reason I can think of as to why your current health insurance wouldn’t cover you is that you may be out of the country during portions of the cruise. In most cases and areas, I believe, out-of-network considerations will still apply in the Caribbean. But check with your insurance company for verification and details on that, too.
I’ve never bought travel medical insurance and we’ve gone on two cruises already this year. Just do your homework ahead of time and make sure you’ll have the coverage you need in the locations you’re going. Congratulations, Tim!