passport on caribbean islands

[ezemoney]

hello,

i have a question for the more experienced eastern caribbean island cruisers. first off we our on the radiance of the seas on an eight night on a bump out balcony room. we our going to san juan,st.tom,st.johns,and st.martin. i think i have read on one of these islands if you take a ferry to a near by island you will need to have your passport with you to get back.
is this true and if so can you just bring a photo copy?

any other advise will be welcomed.

later,

ezemoney