When I first got the boat I was sailing in the famous Race out by Fishers Island. There were about 20 small boats with guys fishing. I assumed that they were NOT anchored although the depth there might have been in the 20' range.
So I sailed skilllfully right through the lot and snagged one guys anchor line. Boy you shoulda seen his face as he began following me!
I had to cut his line... take his address and send him money for new ground tackle. WOW that was embarrassing. Luckily no one got hurt and no boats were damaged.
I now stay away from these guys with fishing poles out.. some are drifting and some may be anchored and usually right in some channel or fairway.