In reply to sjc: I bet with an elastic band, or some duct tape and a sling, you could bodge this really easily...
for kayak rescues, paddlers often use a "paddlehook" whereby you tape a krab to a paddle (or other stick), in such a way that when you pull the stick away, the krab remains attached, and closes.
its definitely in franco ferrero's book "whitewater safety and rescue (pesda press, 2006 i think) but should be online aswell.