"A hole" in kayaking is when the water is moving as a recirculating hydraulic. It is like a washing machine, the water is just recirculating around the top of the hole. A theory states that you should take off your PDF and dive as far down as you can until you are out of the hole. Mike Desrocher of Water Ice Rescue Training, says that this is not safe and should not be done because to do so you need to take of your PDF.
The best thing to do when you are trapped in a hole, is to curl up in a ball, as small as you can and hope that the hole will toss you out. I really liked this article because if I were trapped in a hole I would not have known what to do, and would have panicked. I recommend this article for anyone that is a beginner at whitewater kayaking.
Ian Merringer, Explore Magazine, http://explore-mag.com/4486/skills/how-to-get-out-of-a-hole-when-kayaking