Speaking from experience here, lots of it. Not once or twice but many times.
I bring chips and cards in every cruise and get games going. In the library, main dining room, private rooms, basically anywhere you can find the space except the casino.
I put ads in the daily paper thing, I send in invites to the daily morning show and they read them. I post flyers on the dining room doors. I openly recruit at the poker table for players while I’m playing in the casino.
If you ask the dining people will set up your tables for you.
They don’t really care what you do as long as your not bothering other people. It’s a cruise ship, it’s about relaxing, not busting paying guests balls about stupid shit.
Just be cool, don’t get drunk and loud.
It is hit and miss on attendance, I’ve had cruises where we payed every day we were at sea and I’ve had cruises where I couldn’t get a single player to show up. It’s kinda like the casino poker, it is either a go for the first day or you can’t get a game up the whole cruise.