All aboard.

With help from the renegade Great Blue Herons (who may or may not be in league with the Great White Herons), Andy was able to track down Mark and the boat belonging to Salty and Sour.  Yup, it's really easy to sneak aboard unnoticed when there are only two people on the boat, and those two people both decide to take a nap at the same time.  (I'm guessing this is their first kidnapping.)  I was also under the impression that old Salty was supposed to get rid of Mark, not just sail for an indeterminate distance and then stop, set up a gangplank, and wait for Rabbit.  (Salty, Salty, Salty.  I'm not sure that Rabbit will give you the money if you don't do what he wanted you to do, i.e., get rid of Mark.)

And while Mark seems to be happy to see Andy (and to a lesser extent, the Jack Elrod ball, which has done more about both the fighting ring and the disappearing wetland than all of the other characters combined), unless he has a knife or steel jaws or acid drool, I think Mark's still in pretty much the same position he was in before Andy arrived (though now, at least, he does have some company).