Read the disclaimers. He gets support from the crew as required by OSHA regulations (or something to that effect). He is presented with survival challenges so he can demonstrate survival techniques. In fact one episode on this marathon showed a crew member reaching out a hand to keep Bear from falling off a cliff he came upon suddenly. Personally, based on the way the show progresses, I think he maps a route ahead of time and knows beforehand if a route is safe or not and where it will take him. That is he knows he can make a raft and travel, say, north for five miles to reach an inhabited island, travel inland through this or that terrain to reach a stream, that will in turn lead him to a river that leads to the village where his pickup awaits. Not 100% certain Les Stroud doesn't do this on Survivorman but his show seems to be a bit more genuine although some of his techniques are more drama and less practical, such as making a fire from your incandescent - I'm sure I mispelled that word - flashlight. Great at destroying flashlights, not so good for firestarting.
As far as the enema goes, I will quote Glockaroo - "icky." Also hard to administer with the size tube he was using and no mention of any lube. Definitely last resort stuff here, and not for the squeamish or untrained. Yuck. i'm glad someone answered my question about using salt water before I asked. Good to know.