[Nexus7]

speed150mph gave an extensive description already (I wonder what p7p8 considers wrong?).

This is exclusively for subs:
Classification in general is a difficult task, perhaps more difficult than TMA. Using NB with spherical, hull, and towed array will help discriminate. To listen at the sound is a good idea, I've never used it as a classification tool, I assume it requires the experience. Does it really function for submerged too? Gotta try.

It was not mentioned but the DEMON can give you the number of blades of the contact's propeller; gotta remember that depending on signal strength you might not get all the "lines". USNI reference usually contains that info for the modelled platforms.
Perhaps weird, but the HF sonar is another visive classification tool. Is the target deaf, HF sonar can be a classification tool, especially interesting for sumberged.