As far as I know, there is no apparatus that would be able to salvage an engine for example sitting at the bottom of the Atlantic.
The Americans were lifting Russian submarines from the Atlantic in 1974.
Glomar Explorer
Recovery efforts began on June 20, 1974. The 63,000-ton Glomar Explorer located the wreckage on the seabed at a depth of 17,000 feet (5,200 m).
It may take a lot of time but it will happen.