Were you ever in a space like this? Were you ever in this space in this submarine?
Makes me think of a brig, certainly not a recreation area. Seldom used equipment or stores would certainly be placed down there before a run. Admittedly, it does not even look U.S. - are those prestressed concrete bulkheads or rubber padding?
A holodeck, of course, is a simulated reality facility located on starships and starbases in the fictional Star Trek universe. Is the space shown a simulated submarine flooding compartment? Another place to test for claustrophobia? Lower level reactor on a foreign nuke?
"Nothing quite says Halloween like SUBMARINES"
One of you may have been there personally, know someone who was, or recognize the photo and identify it. Otherwise, don't hold your breath, it's strictly a trick or treat proposition.
Submarines are always silent and strange.