From my understanding, the individual didn't actually leak the nuclear submarine's location (I believe it has been confirmed that he was on a strategic US nuclear sub) because the photo wouldn't have metadata (it seems GPS doesn't work under water and reddit strips location metadata).
That being said, it is height of stupidity to post any pictures publicly from a security sensitive location. Just engage in the forum discussion and don't mention where you are located. This is common sense stuff even if you are not on a nuclear submarine.
I suspect his leadership will get the word of this and limit his time dedicated to CK3 and computer games. :)
