If you lay a line from A to B, is there a way to retrieve a line from B?

[Celt]

The situation is as OP described in the post #3, It's not looking for a lost object, it's not navigating around a wreck. The skipper has dropped a shot line to the wreck, but he's missed the mark. The instruction is something like "OK, the shot is 15m NE of the stern, so when you hit the bottom, swim SW and you'll find the wreck".

There's current, its deep, and vis is only 5m, so easy to miss it, or at least waste time looking. If the dive plan is to do a free ascent with a DSMB, there's no need to return to the shot. It's a large wreck and the plan is to start the dive at the stern and end at the bow. So you don't need or want to get back to the shot.

Personally I’d use my compass with a large wreck 15m away and allow 5 degrees for drift in the bearing to stay up tide of the mark. But for a small target, you could take both the reel and the end of the line in a bite around the shot. Run out 20m or so on the bearing well uptide and drift on to the mark. Clean the end of the line of any clips or carabiner and reel in. Make sure to take the line around the shot so that when releasing it drifts down current.