Do you mean to mark a reef once you've found one? Or let the rig float in deep water until it stops moving because the sinker touched bottom?
The first is very common; the latter would seem to be a very time-consuming way to find a reef. Trolling a lure would be ever so much more practical and potentially productive.
Not to mention the fun of hanging the lure up on the reef and losing it!
I'm all for a depth finder and hand-held GPS to locate and re-locate. (Guess that might not qualify as low tech, though.)