Also, some of the wrecks can be salvaged for low-background steel, which has had some extra value (not sure if that's still the case.) This is often not legal

Also, some of the wrecks can be salvaged for low-background steel, which has had some extra value (not sure if that's still the case.) This is often not legal -- the wrecks are war graves -- but it has happened nonetheless. There have also been advances in algorithms for estimating where ships have gone down, so-called "renavigation". This has enabled search areas to be reduced in size. This was used to locate some of the carriers sunk at Midway.