The Mooring got a doctor to come onboard as soon as we returned to harbor after our capt report to base that we had a positive emed antigen test on board. Dr. tested everyone, still just the one positive, but indicated they would be back tomorrow to PCR test everyone. We raise objection by showing our approved USVI entry permit. Next day Mooring official came onboard and said the negatives could all leave, but the positive would have stay on board for PCR test at noon. The problem could have developed that the antigen positive could have tested negative on PCR but we would have already gone by water taxi. It would have been okay for us since no one was flying out of St Thomas until next day, but if you were catching a flight same day as returning you would have missed flight.