Yes, the stunts are unbelievable. That's the point. The first Indiana Jones films were a tribute to the serials of the 1930s: the hazards were insane and the hero came out with nary a scratch when by all rights the first blow should have killed him. Kingdom of the Crystal Skull has layered on aspects of the "B" movies of the 1950s, when the country was obsessed with aliens (Sci-Fi Dine-In at Disney Hollywood studios runs the trailers) and Communists. It works perfectly.