There is a downstream current under the hydraulic at a dam or smooth ledge in a river. It is absolutely counterintuitive but you need to sink and grab that bottom current to get out. At times I've been able to work back and forth and finally punch out the end of the hydraulic but if it has you and you can stay upright I've popped the sprayskirt on a kayak and sunk the boat enough to be drug downstream, or bail and dive. If you keep recirculating the river will win. Never walk in rushing water, the chances of foot entrapment are really high. Once that happens the current will push you over and the last 2 minutes are doing pushups off the stream bottom. Keep your feet up and float to calmer water.