There have been a huge number of studies showing it at R0 of 2.2 or even higher in the early outbreak stages.

The range given is 30-70%.

This is from an article about modeling this in Nature.

For a completely novel pathogen, especially one with a high (say, >2) basic reproductive number (the expected number of secondary cases generated by a primary case in a completely susceptible population) relative to other recently emergent and seasonal directly transmissible respiratory pathogens, assuming homogeneous mixing and mass action dynamics, the majority of the population will be infected eventually unless drastic public health interventions are applied over prolonged periods and/or vaccines become available sufficiently quickly. Even under more realistic assumptions about mixing informed by observed clustering of infections within households and the increasingly apparent role of superspreading events (for example, the Diamond Princess cruise ship, Chinese prisons and the church in Daegu, South Korea) at least one-quarter to one- half of the population will very likely become infected, absent drastic control measures or a vaccine. Therefore, the number of severe outcomes or deaths in the population is most strongly dependent on how ill an infected person is likely to become, and this question should be the focus of attention.

https://www.nature.com/articles/s41591-020-0822-7.pdf20% is very low and very unlikely end point.

As reference, 2009 H1N1 had an R0 of 1.3 and ~24% of the world got that. Simple log model suggest 45%.

The simple log model for R0 of 2.2 is 85% infected. I was “de-rating” with a ~50% estimate.

To be clear on a cruise ship you’re more likely to approach the theoretical limit, since it’s a small population and there’s no good way to prevent the spread.