Ninthace,
There would be gravity signature, or anomaly as we say in the trade.
For modeling purposes and ignoring the ballast tanks, think of the pressure hull as a steel cylinder full of air. It will have a different bulk density than the surrounding water.
PS I’ve just done some calculations, based on an Ohio-sized cylinder and I calculate a density of 2.3 gm/cc. More than I expected. I guess reactors and missiles are heavy!