We started our current trip with three cats whom we have served for a number of years.
Cato adopted us about 5 years ago, is a Siamese cross, brown/white, and about 6 year old male.
Cali was a rescued farm cat (with kittens) She is about 14 now, and a Calico female.
Fraulein was a tabby, born in our master bedroom 18+ years ago, but we had to put her down two months ago in Puerto Vallarta, she just declined at a rapid rate in a short period of time.
All of them adapted well to boat life. Fraulein is the only one who showed any interest in going off the boat at the dock. Cato fell overboard once in LaPaz while chasing pelicans off the boat. There was a super current running, and we're lucky we knew he went overboard.
Cali has zero interest in getting off the boat. She's totally bought into the whole "kept cat" scene.
If you travel to places with lots of Bald Eagles (like Alaska) care should be taken to keep them inside, as they (and small dogs) have been known to have been taken off of boats by Eagles.
All three have also RV'd extensively with us over the years in a 40' diesel pusher motorhome, and then on the boat for the last 2.5 years and 8000 nm.
Cali does get seasick in a bad seaway, but we have meds for that the work really well.
We love traveling with our fur babies. Two litter boxes and the boat doesn't smell of cats at all.
International travel CAN be a bit of a headache though. We keep their vaccinations up to date, with a shot record, and health certs, and haven't had any issues yet, but it has prevented us from going into several countries due to horror stories we've heard.