Holy shit, I just came across the weirdest glitch I've ever seen while playing this game.
I just started up the game and it spawned at the house. I grabbed the speedboat there and floored it to the airport, and about halfway there the camera suddenly shifts to some ridiculously high point in the sky (while still moving forward at the same speed) and on the minimap, I'm apparently somewhere on a snow-capped mountain even though in reality I'm still in the ocean several kilometers away from the nearest coast. I jump out and I collide with an invisible mountain and tumble down. Now I'm standing on this "mountain", I basically repeat this jump/tumble until I reach the bottom and, on the minimap, I'm in a grassy field near some roads. When I walk, you can even see a faint trail of grass, as well as footsteps, following Rico as he runs in midair across the ocean. The effect looks like something out of Okami.
At this point I'm near water level and on the minimap, I see a shore not too far away, so I run in that direction. My speedboat is floating in midair and I try to grapple to it, but I keep colliding with invisible walls. I give up trying to reach that and just run for the water. I notice a wave texture on the water, which indicates the shore, and at this point it looks like I'm running on water. That Tiger Woods Jesus shot has nothing on this. I reach the water and he starts swimming, so everything looks normal. The minimap still shows me in a completely different location, and every time I reach a small island on the minimap I run on it, but that's about it. So I continue swimming towards the airport and after a few minutes, I notice that the minimap has a solid white line, with nothing but white past that point. When I reach it, Rico dies and literally shoots up into the air with his back straight and his arms extended to his side. His hands and head were completely limp. He couldn't have looked more like a crucified Jesus if he tried. At this point his body was ascending really fast and everything was turning white as the screen did that usual fade-into-red effect you get when you die.
God I love this game. I wish I could've recorded it but I was playing the 360 version. Come to think of it, I probably should've gotten my camera and just recorded it off-screen.