I just recently returned from diving out of Boynton Beach where we had some fairly strong currents at the surface so rather than towing the flag, the flag was towing us. The diver with the flag was pulling pulled so fast that the rest of the group were challenged to keep up.
Our solution was adding a reef hook to the end of the line and used that to anchor in at different spots long the dive to keep the group together. Worked quite well.
Was watching a lobster diving video earlier and saw this set up. Looked like a standard cave reel with a reef grapple where you would normally see the clip attached.