I work in the travel industry, and there are some international river cruises that do not require vaccination. Nile River comes to mind. Most of my clients refuse to get vaccinated, so I plan trips that are easy for them. MSC Cruises does not require a vaccine at this point, and most luxury/yacht cruise lines aren't enforcing the requirement. Carnival Corporation - Princess, Carnival, etc., as far as I know (last updated Thursday) is up in the air about requiring it. MSC just requires a negative test to board and have several out of Miami on the books.