You seem to be describing the nautical equivalent of a corporate function or wedding band, doing covers that people will recognise and want to dance to, perhaps in one of the bars onboard in the evenings, and to add to the general festive atmosphere when the ship leaves port, etc. No need to have all the songs note-for-note for that, more important to be together with however the rest of the band is playing them, but I would at least try to learn all the hooks and key riffs (especially if playing any songs that have a well-known bass line).
Sounds like you're not the house band that supports other guest artists for evening shows, unless you're doing double duty, in which case for those shows I would expect you'd be given charts and would need to play whatever parts were written on the charts even if different from whatever recordings you might be familiar with.
Sounds like you're not the house band that supports other guest artists for evening shows, unless you're doing double duty, in which case for those shows I would expect you'd be given charts and would need to play whatever parts were written on the charts even if different from whatever recordings you might be familiar with.