When we hunt in waters that are known to have sharks we use a lift bag and send each fish up to the surface as soon as they are shot. Someone on the boat gets the fish out of the water and we never have to deal with curious sharks. If you are alone Which sometimes we do, we send the lift bag to the surface on the anchor line. Every once in a while we will lose a fish if it is on the anchor line, but never when someone is on the boat.
I'm not sure where your friends are fishing, but let them know it is illegal to possess a bang stick on FL reefs, and if they get caught they could lose all their equipment including the boat they are fishing from.