We use disposable aluminum
roasting trays (one) set into the toilet.
A very little bit of litter, and frequent emptying, including immediate feces removal
They'll take to it immediately. You could also try one of the commercial
train-your-cat-to-the-toilet contraptions before you leave, and maybe it wouldn't be necessary for the pans. We tried to do it without, and failed, but there was NO question that they went right to the head
Non clumping, and once we reached the Bahamas
, it was all beach sand (with litter aboard when we weren't there or able to get ashore)...
A clue for their comfort with cruising will be to get them to an open anchorage for several days, where the motion of the boat, without your being under way, will acclimatize them to the motion.
Portia would absolutely revel in the sound of the anchor
going down; she knew that the passage
was over. Conversely, she'd dive for the berth when she heard the engine
start, until we were under way.
Cats thrive aboard, and are not any real difficulty, other than that you'll want to make sure they have an accustomed place to scratch. In our case, it's the bottom of the mast
which we've wrapped in light line.
If you're worried, take them out boating
every chance you get...
PS Portia and Greta are ashore being service animals
for Lydia's mother, who cruised a couple of times with us, both with Portia. We gave her Portia when she came to the US to go cruising but got too old while we finished the boatyard stuff (2011-2012 refit
in the gallery).
Our shakedown garnered Greta; when we arrived on Christmas
Day 2013, she moved off the boat to be with Portia. When her mother is gone, they'll come cruising with us again.