When you reach the water with Sam and Mike, hop in and follow the left wall to find another ledge you can climb onto. This is actually where you'll find the final Twins clue, the Scrawled Journal. Read it to learn the true identity of the Wendigo - it's imperative that Josh learns this.
Save Yourself, Part 2
When Matt finds Jessica in the mines, you'll be pursued by yet another Wendigo. Hide when you have the option, then continue forward. You'll then have a choice to hide together or abandon her. Stick together, and you'll both survive the encounter. Matt and Jessica are now safe for the last leg of the game.
The Result of Chaos
This is it, the final hurdle in getting everyone else through this insanity alive. A pack of Wendigo will invade the lodge with Sam, Mike, Chris, Ashley, and Emily stuck inside. Don't bother to lock the door on the beasts - run with the others to the living room. These final moments are key. The Hannah Wendigo will actually kill off a few of the other monsters, but you need to stay completely still when the game calls for it.
When asked to save Mike or run, save Mike; when asked to run or hide, hide. This will let your friends slip out the door. You'll then have one last choice to run or hide - hide. In between all these choices, you'll need to stay still (during the game's most intense moments, I might add). And Josh? You'll see a credits stinger revealing him to be alive and well. Well, he's become a Wendigo, but at least he 'survived.'
At this point you should unlock the Four Daughters Of Darkness, The Quicker Man, and They All Live trophies - congratulations!