I had one of the lifeguards/beach/security guys ask me last time for my Dry Pak before I left. Lots of people along the beach have them but apparently they are very expensive in Negril. If you want to give a non-cash gift, I think these would be good for those who are outside all the time.

http://www.amazon.com/gp/product/B0065TKDD4/ref=oh_details_o00_s01_i00?ie=UTF8&psc=1