Ah yes. I think I've commented on this one before. The silver that fell off of the Harold. The problem was that during the salvage attempt, they used a clamshell bucket to retrieve the ingots. And while doing so, they kept pushing bars deep into the mud. And now you have to worry about a layer of toxic sludge thanks to the industrial revolution of the early 1900s.
This actually happened more than once in the area. The same thing happened to the barge "David Sturdevant" previously in 1871 when the barge was hit by the S.S. City of Manchester. The $30,000 worth of silver ore fell off of the barge into the mud and the barge itself was recovered and scrapped. I know they sent divers to recover the silver ore but I don't know how successful they were. This was in the narrows off Staten Island in about 72' of water.