A few years ago, spent a super weekend anchored some 50 metres off the base of the High Island Reservoir's Dam - Yuen Ng Fan (元五墳)in HongKong's District of Sai Kung
See the link :-
DAM
On the Sunday around 3pm decided to weigh anchor and return to our berth in Pak Sha Wan only a few nautical miles away. Cleared the cockpit, secured the dinghy, stored the outboard and fuel tank, Cleared the cockpit and decks. Checked all lines on board, started the engines, alerted everyone on board. Coxswain moved the boat slowly forward, while I reeled in our 30kg (66lb) Bruce anchor with my foot on the anchor windlass button. Gradually the anchor chain moved aboard until I could actually see the anchor and something that it was attached to. The 'something' was a steel net of cables, that had been used to contain thousands of rock boulders which formed part of the dam wall. No ways was my Bruce going to let go of its find! Tried every which way to release the Bruce - Shortly before sundown a Chinese fishing trawler was passing by on its way back home and noticed our predicament. They were able to attach a line to the steel net with their power fishing net windlass and lift the net - which enabled us to free the Bruce.
A couple of beers, a couple of Scotches and thanks to our new friends, and they were on their way home to Sai Kung's Trawler anchorage.