I always have my swim toys when I travel south (mask,fins,snorkel). I bought a pair of mini fins which work fine but take of way less space. Other things I have on my always list is a good headlamp with extra batteries, small pair of bino's. I have an issue with sunglasses (they seem to walk away) so only travel with cheapos unless I have serious fishing planned. I gave up trying to catch fish in Jamaica so the fishing gear will be staying home. But since I am going to Jamaica, will be picking up a new pair of small sharp scissors (if you have to ask, don't lol)
So what are your must have items?