COVID is being treated like any other illness in the UK and many other European countries.
If you feel ill don't mix with others as if you had a cold or the flu. Only a small minority are at risk of developing a serious case and that's the risk you run with any contagious illness. Wash your hands regularly, cover your nose and mouth for coughs and sneezes and keep up with your vaccination boosters.
Enjoy your cruise and Carpe Diem.