My experience (and only my opinions/theories/observations). I have been on 10 cruises with a total of 98 days since cruising resumed (2020). Only caught covid once and it was on a ship (well technically on a bus). Have been "exposed" to several active covid family members, but never caught it from them.
I am positive my covid case was from a very long excursion day on a bus. Symptoms showed up within a few days. Finally decided it wasn't asthma and confirmed by Medical Center and isolated. I was wearing a mask for most of the time when out and about the ship. I felt falsely secure since the weather was nice and I was outdoors.
In my opinion: Today's covid is much more contagious and less lethal. But incubation time is just a few days.
If you get covid:
You are on a 7 day cruise, you will probably test positive when you get home.
You are on a 14 day cruise, you will probably test positive while still on your cruise.
I was recently told (after my sister brought covid to my house after a family graduation in another state) that all she had to do was wear a mask while testing positive and as long as she had a fever (ref: Kaiser). No other restrictions as long as she wore a mask.
Isolate for 5 days from onset of symptoms plus fever free for 24 hours.
Covid is not just from a cruise. Air travel can be a source. Somebody has got to bring it on the ship with them.
I thought I could avoid getting it since I am vaccinated to the max and still wear a mask when in crowds or around people I don't know well. I am in the minority. But the two states I am in have higher than average cases of covid. You will see a lot more people wearing masks in Honolulu.
I am not about to stop cruising or traveling. I am just cautious and proactive. My case was very mild. Some are not as fortunate. I believe Covid is hear to stay.