We were on a river lining boats and there was a big boulder in the way preventing an easy way to pass the boat to the group downstream. We let the boat go (with a line attached to it) and a relatively simple gadget, a carabiner clip on a pole was a great tool for reaching out and grabbing the boat in the middle of the stream. As soon as the beaner clipped it detatched from the pole, giving you a line to your midstream boat
Some good river rescue gear on this site.
The clip is featured on the right and uses a common telescoping extension pole you can get from any home depot. You dont lose your carabiner either