-- Last Updated: Dec-05-12 5:37 PM EST --
On whitewater runs I virtually always have a throw bag and I usually do even on Class I river paddles. Since I usually am paddling an open boat, the bag is pretty accessible. I have one that attaches with a short length of 1" nylon webbing that is secured to a D-ring between my knee pads. The bag is stuffed underneath the front flotation bag but can be quickly pulled out. The nylon webbing strap has a nylon quick release buckle on it. I find that the bag can be released quicker and more easily using the quick release buckle than it could be if I secured it to the D ring with a carabiner.
On training runs we sometimes will do rope throwing practice at lunch stops. If you want to get some real life practice and live near the southeast, go to the Nantahala River and stand on the rocks at river right below Nantahala Falls on a weekend summer day. You will have many opportunities to try your hand at reeling in swimmers.
As for making a second throw, I have never been able to retrieve a throw bag rope quickly enough to make a second throw to the same swimmer. I have occasionally been able to be quick enough to make a throw to a second person swimming after the first. If I attempt a second throw, I coil the loose rope in my left hand as if it were a throw rope rather than a throw bag, and quickly stuff just enough rope back in the bag to give it enough weight to throw. The bag I usually use has sides made partially of mesh (as many do) so it really wouldn't retain much water.
Sure, it is possible to throw a bag from your canoe. You usually have to throw side arm or overhand rather than underhand, though. The problem is how to anchor your boat so it doesn't get pulled downstream after the swimmer. If you are near another boater, that person might be in a position to belay your boat while you make a throw.
As a matter of fact, my friend, known as Pyker here, did just that on the Lower Youghiogheny River a couple of months ago to haul our friend out of the current while I grabbed his canoe with one hand and a rock with the other.
Years ago, my friend Hugh Worthy was leading me down the Little River in the Smokies above the Sinks. My paddle got snagged in Big Sycamore rapid and was stripped out of my hands and I swam. Hugh was sitting in his boat in a shore eddy near the bottom of the rapid and threw me a rope and hauled both me and my boat in without getting out of his. I have no idea how he did that but I suspect he must have wedged his paddle into some rocks with one hand, and deployed the rope with his other hand. But Hugh could do things ordinary men could not.