I cruised the Alaskan sampler in early may on the discovery. As I was going solo, I ate almost entirely on deck 16 and nearly always outside by the main pool or aft pool deck. I wore a mask in all public areas that was not N95, but a double layer cloth mask with a microfiber layer. Not sure if that's worth anything at all.
I never ride the elevator on ships, and this was no exception, but it really makes me detest how large the royal class ships are. I had booked a cabin on deck 16 but was upgraded to a balcony on deck 8. It was very nice to have a balcony but with pretty minimal outdoor areas on deck 7, I spent most of my time on the upper decks.
Since the incubation period is about 5 days it seems, I think the odds of contracting covid while enroute are higher than when onboard. For most, that would align with showing symptoms on days 4 or 5 of your trip.