Maybe instead of telling him about this thread and asking him to take advice from a bunch of people he doesn't know you could get some info off the internet. Simply google drinking water in jamaica or something similar and you'll come up with tons of info that is factual and may give him more peace of mind than just the advice of a bunch of folks on a message board. Granted, we've all "been there done that" but we are strangers nontheless and he's had some rough experiences and that speaks much louder to a person. Try getting him some good, solid facts and maybe he'll at least be tempted. Or perhaps he'll keep it in mind and when you guys get there and he sees others eating and drinking so freely he'll put the two together and relax.