At sea
Later when the weather improved, he would dash around on deck chasing flying fish and each morning I counted it a small miracle if he was still on board. I had tried clipping him to a safety line at first but he got so hopelessly tangled around winches, etc. and seemd so unhappy that I decided to let him take his chances. Seven years, and quite a few duckings later, he has become super-cautious except for the occasional mad frenzy which most cats seem to perform either triggered by the full moon or some other primitive instinct.
Life aboard
Fortunately his unplanned swims have all happened when we were anchored or tied to a dock.
He spends most of his sea-time in his bunk where he feels secure with cushions and often uses the leecloth as a hammock. On deck he has learnt to avoid the leeward side deck and likes to shelter under the dinghy on the foredeck.
His sandbox has to be kept below when we are sailing as the cockpit floor is small and often gets wet. Sheets that have been trailing in his box become quite awful to handle. I find that coarse beach sand works very well as the very fine sand clings to his paws when he steps out of the box and then gets tracked all over. In the absence of a handy beach I have to resort to the expensive option of commercial kitty-litter.
Diet
His only hunting opportunites have been harvesting those flying fish that land on deck and the (very) occasional cockroach. So I have to provide his food. Rather a fussy eater like most cats. This is possibly one area where a dog is a more suitable cruising pet. After a lengthy stay on the US East Coast he became rather fond of the gourmet catfood available there. Now, in Brazil, where wonderful steak is cheaper than the tinned garbage which passes for cat food, he refuses to eat either. Fortunately he has grown used to the dried pellets which seem to be universally available, although I don't know how healthy they can be.
Pros and Cons
Would I choose to take a cat with me again? Yes.
Of course there are disadvantages but these become a problem only on rare occasions and the day-to-day pleasure I get from Sinbad far outweighs these inconveniences. So far the places I've visited have not had draconian quarantine regulations. My main problem has been finding someone to look after him if I need to leave the boat to visit family or travel inland.
Something else to bear in mind is that not all cats are created equal. Sinbad is very adventurous, will happily hop in the dinghy to be dropped off on a cat-sized island, if one can be found, and can be left there for an hour or two. He is usually quite ready to go back on board when I return to fetch him.