When I was reading about Cuba around the time I visited there (2008), I got the impression that the only way in is by air.
Now, as of 2012, is this (still) the case? Or are there any cruises, ferries, or other sea travel options for reaching Cuba, legally, from some of the nearby counties? (Either for a day-trip or a longer visit.)
I mean, Mexico is close. So are Jamaica, Bahamas, and many other island nations. (And Florida, of course, but I suppose we can count that out for now.) You can easily fly to Havana from e.g. Kingston, Nassau, or Cancún—it'd only make sense if you could take a boat too.
Image from Bing Maps
(For the purposes of this question, assume that the Cuban tourist card/visa is already sorted out.)