I'm not advising anyone doing it, but isn't there a path around the lagoon? Could swear I've seen one from the Monorail (I'm talking past the GF, not just path from Poly to GF). Maybe it doesn't go all the way?
Edit: Nevermind. I forgot about the canal for the water pageant boats. You'd have to swim it or jump it, lol. But there is a path past that point to MK - not sure why?