So now that everyone is safe, how do you go about unpinning a raft that is being held down by a at least a of ton of free flowing river? There are several techniques that our guides are trained to use such as the "10 boyscouts" or dirct pull method, vector pull and z-drag. For most of us knowing that our guide knows what they are doing and has the training to implement these rescue techniques is enough. For those of you who are interested in a more thorough explanation see the end of this post.
Most companies train their guides in rescue systems, but learning these systems once isn't enough for most guides to be able to recreate an effective z-drag when it counts (when there are guests sitting on a rock with a partially submerged raft nearby). That's why we hold training sessions several times each year to refresh our guides rescue skills. We make these trainings fun by including an element of competition - such as during our "Rope throw rodeo". Guides complete the course earning points for laying their rescue ropes across targets, rescuing "swimmers" and tying knots. The guides also build rescue systems such as z-drags and telfer lowers on dry land to refresh their skills.
All of this training pays off. When there is a problem on the river our guides are usually complimented on their ability to quickly and effectively solve the problem. Being able to unpin a raft if there is an unplanned for situation allows us to get on with the trip - which is after all, what we ventured onto the river for in the first place.
How to unpin a raft
We start with the simplest method first and work our way up. This allows us to be efficient if the raft only needs a little help to slide off of the rock and keeps everyone safe - the more complex the rescue system the more potenial for problems. The guide simply starts to pull on the raft at the most likely looking place. The object is to try and dump most of the water out of the raft to allow it to refloat or to use the current to "wash" it off of the rock that has it pinned. If that doesn't work we attach a rope and add more guides to help pull - the "10 boyscouts" method.

If we still can't move enough water out to unpin it we use simple physics to increase the efficiency of our pull - the Vector pull.

Finally we move up to building a rope system - the z-drag. This system works just like a pulley, giving us a mechanical advantage to increase the amount of force we can apply to the raft to allow it to dump the water holding it in place.

If you're interested in the technical details of raft rescue then River Rescue: A Manual for Whitewater Safety ISBN 978-1878239556 By Slim Ray and Les Bechdel is a great resource.