I too am amazed and wonder why such an area is not secured.
Having a sign that says " crew only ' isn't a deterrent to an idiot like this.
Too bad he didn't get tangled in the chains and got overboard with the anchor!
If some drunk pulls a prank like this on a ship on the open seas, then what kind of danger might he place the innocent public in ashore when he gets drunk and out on the streets and roads?