Originally Posted by Wightdiver
We used to have a large buoy with a 4 inch stainless ring attached. Run the shot line through the ring, attach it firmly to the back of the boat and then gun it. As the buoy move away from the boat the it drags the shot upwards, you then need to quickly pull in the slack before the shot sinks again. I think our shot was only around 25kg.
I use a similar method for crab trap retrieval. A 12" or 14" (don't remember) Polyform ball buoy with a 6" ring goes on the trap line, then motor off about 45 degrees away from the trap direction (i.e. if the trap buoy is hanging due south, you head towards the traps, but 45 degrees off, so either a 045 or 315 heading.) The drag of water on the buoy will suck the buoy under, which will raise the trap (it does put a lot of stress on my wire traps, though; they're only like $29 though, so are replaceable to some degree.)
You can get a better explanation by searching "ball buoy anchor recovery" or similar.