The submarine used in this episode is a former Soviet U475 (Foxtrot-class) built in 1967. She was retired from active service in 1994 and was berthed at Long's Wharf, Thames Barrier, where the episode was shot.
The wreck that Ed finds whilst searching for the submarine is of a real Dutch tanker named Callisto, which sank in the North Sea in 1959 after colliding with another ship in thick fog.