Louise--who knows at this point?????? This is the link to the official government website, which shows the requirements. As to whether it's 120 or 72 hours for the RT-PCR test, that is open to question at this point.

For the antigen test, this is what is says, if the site can be believed. "Alternatively, travelers originating from a country that is categorized as high can do an antigen test for the SARS-COV-2 virus obtained from a naso-pharyngeal swab performed within 48 hours prior to departure to Sint Maarten. Only the following antigen tests are approved: the Becton Dickinson (BD) Veritor Plus, the Abbott Panbio, the Abott BinaxNow and the Roche/SD Biosensor F antigen tests. Tests performed outside of the 48 hours period or other brand and type of antigen tests will not be accepted." For the Antigen test, they are not allowing other types of antigen tests, so check first to see if you can get the proper kind of antigen test and if not, then the PCR test is the only way to go.