We never had problems with Caribbean customs
officials. Jet Blue, however, forced my wife to buy a return ticket even though she had with her all of the relevant paperwork from entering St. Lucia on our boat. The people at the ticket counter were simply unable to wrap their minds around the concept
of flying in and sailing out.
Next time it happened my son was flying in to join me in the Bahamas
. I found a $90 fare back to Ft. Lauderdale and just bought him that ticket. They did ask to see it and it worked - There is no need to buy a complete return ticket. All they care about is that you leave the country you are flying into. So, for ex. you could buy a ticket on LIAT to the next island up the chain and that would do the trick too.