Had a PCR test this afternoon (leave for SXM on Thursday morning.) I too thought it would be the one up into the brain, as you put it, but it was actually just a thorough swab in each nostril (about 10 seconds in each). Not bad at all. I assume this may differ depending on the test site, but it was a PCR test. My understanding is either PCR or antigen test are acceptable for SXM, but you need to do antigen within 48 hours of departure to the island, while there is a 120-hour window for PCR.