I was on a ferry recently and the journey is lovely.. And the beds very comfy..I slept like a log
And I've been on the ferries too
One trip was a smooth as a millpond and comfy as heck, few days later it was as rough as hell, people throwing up everywhere (literally) and staggering around like drunks
(fortunately not me!)
I'm just saying in my opinion it wouldn't be a sensible way to travel for a heavily pregnant, feeling crap, lady.
Why I put sensible in a comment about KP though I just don't know