Every cruise line has their own rules. As of a few days ago Azamara were quite specific on pre arrival testing (see comment #18) either one day antigen or three day PCR. In fact Blue Star Ferries issued the following a few days ago. Apart from wearing a mask, no vaccination or testing required.
We would like to inform you that according to
Government Gazette 2369/B/14-05-22, for the
movement of passengers, it is no longer required to
present - demonstrate documents proving the
vaccination against coronavirus COVID-19, the
recovery from the disease or a negative laboratory
test result after coronavirus COVID- 19 testing.
The use of a protective mask is mandatory in all
indoor public passenger areas. If a passenger does
not wear a mask, he will not be allowed to board.