MSC is currently doing a cruise in Italy/Mediterranean. Americans are not allowed on the ship. I don't have all the details, but the are testing before they allow boarding, mask required to be worn unless you are eating, drinking or swimming. All fresh air is being funneled into the rooms. Casinos open. There appear to be quite a few people on the cruise. You can probably find the ship using cruise tracker.

I am not ready for a cruise right now anyway, but wondering how they will handle it if someone test positive while re-boarding from a port of call.