GPSOf course, a good GPS with tracking ability would do the job a lot quicker and without the need for markers. Simply mark the beginning of you drift on the GPS and allow the tracking trails to add up. Then you can follow the trails back and drift back over the exact area you just fish, or move over 20 feet or so and drift parallel to you original drift. GPS technology has come a long way since my buoys!
Offshore StructureIn another area offshore, I have a tugboat marked. It is in about 120 feet of water and it has about a 40 foot relief ( distance up off the bottom). Drifting over this monster only results in hung lines and lost tackle. The tug is disintegrating slowly each year, and a debris field has formed around its perimeter. The current has washed sand from under it and formed deeper holes for fish hides.
With this reef, you have to anchor to be able to fish it and not loose all your tackle. On reefs like this one, the idea is to fish alongside the structure, not on top of it. But finding the right anchoring solution is very similar to determining the right drift.
In past years, I would drop a marker buoy right on top of the tug. I often lost the weight to that buoy when it came time to leave. Then I did the drifting routine again to determine where the wind and current would take the boat. At the end of that drift, I dropped another buoy.
With that line of drift set up, I idled up about 200 feet ahead of the first buoy that I place on top of the tug. Then I moved off to one side of the drift line or the other and sent my anchor to the bottom. A long fetch on the anchor line allowed it to set into the sand, and when the anchor line tightened, I would be slightly up-current and just off to the side of the tug. Baits dropped to the bottom went exactly where we wanted them to go, and we caught fish with few lost terminal rigs.