How do you get back to the rest of the game board from these 2 spaces? The boat charter ability only exists in Falcon Point, so how do you get back if you go to one of these 2 spaces?

Someone else on Falcon Pt pays $2 to move you. Or you get lucky with an encounter.

avec said:

This. So be aware that if you go to these locations you might be stuck for a long time. During one game several months ago my investigator was stuck for five rounds!

In my first game I had Tommy floundering around between the two spaces, hoping either to be returned or to be devoured (both of which would be a benefit). Unfortunately he survived and the terror level climbed high enough for him to fail his personal story. Somehow, word got to Tommy that he let everyone down while he was underwater.

That's how Leo Andersen "went" in one of our previous sessions:

he sealed a gate at Devil Reef, then got stuck at that tongue-breaking place for several turns because his teammates were all slow pokes. He was devoured by a nasty encounter just as one of the other investigators was a hair away from rescuing him.