You can view the port visit schedule for Santorini (and other ports) here. https://www.cruisetimetables.com/santorinigreeceschedule-28aug2024.html. It includes the ships and passenger counts. I found this as I am looking at a cruise on Royal to Greece next June and was happy to see that the day in June only had two ships scheduled to visit. Looks like August 28 has four but that might not be too bad (I think they max out at 6 during the peak of summer)