Having dived the Peverill ledges many times I know how snaggy they are! Good lobster & crabs to be found tho, especially close to the sewer outfall!!! LOL
We use the cable-tie method on our anchors. Several strong ones attached & a good old tug will break the chain free which is now attached to the 'Wrong end' of the shaft. You will be pulling the anchor out in a backwards direction! Or if you want to involve more line & a buoy use the 'Trip' method? Home-made grapnel anchors that bend free is what we use to hook a wreck if there is a chance we could lose the shot-weight? Hope this helps?