Eric J. Collenette, Secret of the Kara Sea, 1987
United Kingdom
HMS Orca
S Class Submarine (Modified)
Details as per the real ships
Modifications: "...extra batteries, and some of her ballast-tanks have been converted to carry fuel to give her a surface range of nearly six thousand miles. She can travel one hundred and twenty-seven miles beneath the surface at two knots and nearly ninety miles at four..."
Note: Author explicitly identifies her as a modified member of the S Class.
HMS Scavenger
S Class Submarine
Details as per the real ships
Note: Class determined by name only. Appears only in the first novel in the series 'Ninety Feet To The Sun'.
Plot summary: A submarine sent to support the convoys to Russia is sent to find a missing ship from the last convoy.
Note: The novel covered in this entry is the third in a series of at least three novels centered on a character named Ben Grant ('Ninety Feet To The Sun', 'The Gemini Plot' & 'Secret of the Kara Sea') Only the second novel is on the Internet Archive along with the third. Back in 2016 I covered another of this authors novels 'The Talisman Deception' (1992) which is not part of this series.