Follow the directions to perform the "Get on top of the main bridge in Pagoda" glitch. Once on top of the bridge, look down and line yourself up with the river. Turn around and lay down, then crawl backwards off the bridge. If done correctly, you should land in the middle of the river, still laying down. You will have a clear view of the valley in front of the bridge, and be able to shoot at anyone, but nobody will be able to see you. Note: Be careful when using a grenade launcher. The grenade will detonate on the surface of the water at times.