Thought I'd start a new thread on this, as Annie's OP was getting
crowded....

Years ago I lived aboard a houseboat in Victoria BC.  Many folks on the
wharf had felines.  Granted, most of these folks stayed tied to one
moorage year round, several of them sailed & motered the west coast
quite extensively.
  I never heard of a cat jumping off a boat, although I do know of one
who was lost in a storm.  The most common problem with dock cats was
getting snared by stray, disgarded fishooks.  A couple of people on the
dock became experts at removing them.  A few cats I knew LOVED sitting
on the bow of sailboats while they were cutting through the wind and
waves.
 Unlike (John?) who accuses you of abandoning your cats, I will not
make any judgements.  YOU have to decide whats best for the furballs.
If you don't think they're flexible enough to make the switch, by all
means, foster them out.  Just don't forget, cats are TOUGH and very
adaptable, who knows?  Mabey it'll be the best experience they, and you
have ever had!

Good Luck, Happy Sailing.
Mathew