A few years ago some divers in a Detroit waterway found a concrete block with two skeletonized legs sticking out of it. They couldn’t determine if they were from the mob days or more recent.
I still remember a very nasty scene from a book I read decades ago in which some New York bad guys dropped a victim into the East River with concrete footwear. What made it particularly nasty was that the baddies put scuba gear on the guy and taped the regulator in his mouth, so he’d have about an hour to think things over.
I don’t recall the author’s name, but I never want to meet anyone who’s able to think up things like that.