I wouldn't worry about catching the virus, I would be more worried that if someone was sick on the ship that the whole thing would be quarantined and I'd be stuck on it.
Anyone know what the protocol would have been if those 2 people on that cruise came up positive?
I will take a stab at it being familiar with hospitalized quarantine patients and with norovirus containment on cruise ships.
If the two people on the ship came up positive (or even if there was a strong suspicion they had it) I would guess they'd be removed from the ship in a haz-mat sort of way, perhaps by regular hospital personnel (MDs and RNs specifically trained and prepared to deal with this particular disease) along with an ambulance or flight crew (depending on where they were bringing them, I'd guess a major medical center), and hospitalized, since pneumonia is the deadly issue with it, and they would not have facilities, medications or supplies, etc, on that type of ship to treat any (let alone two) people with that serious of an illness since it involves far more than a ship's medical crew would ever be expected to handle.
Certainly they'd need expert and sophisticated care, and it is very possible the patients would need to be intubated and ventilated for a time (I even saw in some cases they were putting affected people on heart-lung machines to bypass the lungs and allow them time to heal), and there would be many specialists involved in overseeing their care, as well as other staff directly caregiving that are specifically (and hurriedly) trained in coronavirus. (Hopefully the hospital would have all the supplies needed for staff safety, if anyone remembers that a caregiver in 2014 caught Ebola when the hospital did not have the proper equipment and enough wasn't known about protection from the disease at that time - see article below.) The patient would also be kept in a negative air flow room that has two sets of doors and helps contain an airborne illness. Extraordinary precaution would be taken, and I'm sure governmental health officials would even be involved due to all the publicity, as well as press outside the doors hounding staff for info (and staff would be instructed not to say anything). These rooms have negative air flow capability just for this purpose. (Since there aren't too many patients that require rooms like this, regular patients can go in them, but if the negative air flow feature is needed it only takes a flip of a switch.)
After they leave the ship's room would be closed off completely until specialists could come in to clean it, perhaps by order of the government the ship would be taken out of service, and same with the ambulance or med flight, etc.
Then I'd imagine all the other people on the cruise ship would be fairly strictly quarantined to their rooms and probably checked daily or more for symptoms. They would have food delivered to their rooms and such, but not be allowed out, nor anything from the room like dirty sheets, maybe even trash, taken out, etc. This is somewhat what happens even with suspected noro cases, though this, of course, is much more serious and likely to involve an overabundance of extra caution.
Once time had passed and people were allowed to leave the ship, it would undergo a tremendous cleaning. I'm not sure I'd want to be the occupants of the coronavirus room, though, even after a "thorough" cleaning. They'd hopefully just close it off. Bookings might be down on the ship, too.
BTW did anyone see yesterday that caregivers of a coronavirus patient (I believe in China) were attacked, had their hazmat suits ripped off, were scratched, etc., when their family member died?

People are risking their lives caring for these patients, not getting much sleep, and doing their best. They are probably devastated with every death, as well. I'm sure emotions are running very high, naturally, but come on.
This talks about the complexities of caring for such patients, this example being about the nurse who caught Ebola during the course of her work:
https://www.scientificamerican.com/article/how-did-a-dallas-nurse-catch-ebola/