Well it’s been said that the Great Lakes won’t give up the dead. Seriously though, when a body sinks to the bottom it is so cold that the gases that normally build up and bloat the body so it re-floats do not build up. A body can stay preserved a long time in cold deep water, that is if the bottom feeders don’t eat it.
Sturgeon and burbot food in the deep water.
“it’s been said that the Great Lakes won’t give up the dead”
Could explain why no bodies were ever recovered from the sinking of the Edmund Fitzgerald ore ship in 1975.