In a deer-lease bunch of which I was once a member, one of the guys was in his eighties. He only hunted turkeys. He'd drive his Ford sedan down near a stock pond where turkeys commonly travelled through and park so he could shoot from the window. One morning, late, he hadn't returned to camp as expected. A couple of the guys drove down to check on him.
He was sound asleep. Turkeys on the roof; turkeys on the hood and trunklid, and turkeys all around on the ground.
There is a state that some call "hunter's doze", where you sorta snooze without really sleeping. Your senses are at least somewhat alert. I guess the advantage is that you're inert and unmoving, thus not spooking game by small motions. I've done that several times--to awaken and see a buck within shooting distance.