It's not like an Aircraft Carrier or other surface ship where they can sneak off to some secluded location for secret snuggle.
Oh, yeah?
On the Los Angeles Class:
Engine Room Lower Level, outboard each Main Condenser. No one goes back there for hours.
Engine Room Lower Level SSTG Lube Oil Bay Mezzanine. Quite Secluded.
Engine Room Aft, just forward of the ERFW pumps, cozy. Better yet, there are two access ports to the Main Engine support structure that's just great for a nap or snuggle.
Engine Room Aft, outboard the #3 and #4 R114 AC units. Good for a quicky.
Engine Room Upper Level. Nucleonics Lab. Has a door that locks.
Engine Room Upper Level. Behind the Nucleonics Labs, around the 10k Evaporator. Some quiet places, wink wink.
Engine Room Upper Level, Charging Water Storage Tank Mezzine. Nice and warm up by MS1 and MS2, and the humidity will excuse the sweaty appearance.
Engine Room Upper Level, outboard the main electrical switch gear.
Engine Room Middle Level Forward, Outboard the #2 SSTG.
Forward Compartment spaces.
Each officer has a bunk. The captain and the XO have their own staterooms.
The Fan Room deck is covered with neatly flaked out mooring lines. A padded floor, and noisy enough to cover the orgasmic moans.
Most crew have their own bunk.
The food storage room at the bottom of the Forward Escape Trunk.
The supply shack.
The torpedo room is usually quiet.
The Auxilliary Machinery Room is ideal for women who get off on CO2 Scrubbers and electrolysis machines, and especially women who like getting banged standing against a Faribanks-Morse Diesel.
The Battery Compartment for the enterprising electrician.
The radio room.
The Sonar Room.
There's LOTS of places to play hide the submarine on a submarine.