Some more food for thought...did you guys discuss safety and come up with a plan prior to him dropping in? Or was it more run down get on the ledge and then let him fire it. Reason...the ledge looked wicked slippery and moss covered. Perhaps rigging an anchor in the nearby rock would have provided a place to for you to clip to. Safety back up so you could yard on the rope if needed. Also, once he grabbed the bag, you could have clipped it into the anchor (clovehitch to a biner) and followed the rope down to help him. Myself and my crew of paddlers carry a small rock rack in our safety kit (stoppers, hexes, webbing, etc.) when we're creekin. I've used it more times than I care to remember. Was the swimmer wearing a rescue vest? By clipping a biner into the back metal ring as well as near the front buckle, you provide 2 places to clip into in times of rope rescue. A quick tug on the release buck and the belt feeds through, should problems arise with the rescue system. This would have allowed him to rest more while being rescued...a vital component to lasting longer in cold water rescue situations. Just some food for thought and glad things went well.
To air is human, to get big air divine.