Leo is on Devil Reef with a Ghost. Rex moves first, goes to Falcon Point, and pays the $2 to move Leo to a different Aquatic location. Legal?

Tricky… its movement but not on the players turn.

I would say that you would pay 2 dollars and then the inviestigator on Devil Reef needs to pass an evade check. If he fails then he doesn't make the boat and the 2 dollars is lost.

I'd say yes. Call Friend does a similar thing magically, and no one as a target of that Spell has ever rolled to escape a monster, I don't think.

Yeah. Investigator A has to deal with monsters only during HIS movement phase. An investigator using FP special ability uses this ability during his movement phase, so it's perfectly legal summoning somebody via FP regardless of monsters sharing the second investigator's location

I can't disagree with the other answers, however I do tend to interpret rules in a thematic way.

Play however you enjoy it the most.

Krawhitham said:

I tend to do that a lot too. But I interpret it as if the boat arrives just in time for the investigator to make a daring leap across the water and escape.