I was shocked to see tours of the inside of MSC and Merchant Marine ships and see that most people had their own little stateroom (as we would call it in the Navy) or cabin. That’s unheard of in the US Navy, especially on submarines. 
Well, I have only served on submarines so I can only speak to that. But on a submarine, the enlisted personnel only get “racks”, that is to say, just a bunk. On a fast attack submarine, you share your rack with two other people. One is sleeping, one is on watch, and one is doing other things on the boat, and you rotate.
Junior (E-7 and below) Berthing on fast attack submarine
On a Trident (Ohio class) or SSGN (Ohio class on which all the Trident missiles have been removed and replaced with a total of 400 Tomahawk cruise missiles with conventional warheads), the enlisted personnel sleep in bunkrooms, each of which has 9 racks inside.
Trident/SSGN bunkroom
On both types of boats, the officers get staterooms, but they are very different from surface ships. Each stateroom holds two officers. They have the two racks and about 24 inches of deck space, and then a sliding door. The bulkhead in between has a fold out desk and a chair.
LT (officer) sitting in his stateroom on a submarine (shared with another officer, racks to his right)
The only two people who have their own stateroom on a submarine are the Captain and the XO (Executive Officer, second in command, I believe Merchant Mariners call this “First Mate”?). The Captain’s stateroom is about twice the size of the XO’s stateroom. An amusing anecdote on submarines is that there is a tradition where the XO’s door is stolen and passed around to various divisions on the submarine (nuclear machinist mates, nuclear electronics technicians, a-gangers, sonar technicians (like myself), etc.). 
Unlike on a surface ship, most of the doors are just normal doors. On a fast attack submarine, there is only one watertight door; on a Trident there are three (IIRC).
Senior enlisted berthing (E-7 and above) is basically the same as junior enlisted berthing, except they have a separate area.
The crew is very small. Approximately 100 enlisted personnel and approximately 20 officers, including the Captain and XO. The Captain is usually a Commander, but there are some full bird Captains. The Department Heads are usually Lieutenant Commanders, although the Navigator (head of Navigation Department) on my first boat was a very senior Lieutenant.
As far as life on a submarine…EXTREMELY stressful. ok, in theory you have 6 hours on, 12 hours off. IN THEORY. In practice, you could have training after watch, you could have a department wide evolution such as moving torpedoes around in the torpedo room if you are Weapons Department (which I was), there could be a drill, there could be an actual emergency. It was VERY TYPICAL to stay up for 24-48 hours underway on a submarine. This will happen at least once a week, usually five or six days a week. I have personally stayed up for four days doing operations. I kid you not and I speak literally. Luckily, I actually got to sleep for 10+ hours after that was over, which is very, very rare.
As far as ports, it depends on what type of boat. Tridents do not go into foreign ports. They are normally on strategic deterrent missions but sometimes (rarely) do other “interesting” stuff. I got to do the interesting stuff only twice. I can neither confirm nor deny the presence of a nuclear weapon aboard any US Navy submarine at any time. US Navy submarines are powered by nuclear reactors, so we are limited only the amount of food we can carry. I personally have been submerged for 87 days straight (never coming to the surface the entire time). Our boat went to Pearl Harbor, San Diego, and Kachteikan (spell check), Alaska, while I was aboard. I served on a fast attack too but the one I was on was in drydock the whole nine months I was assigned to the crew, and then my EAOS came up and I got out of the Navy. 
So my sea time was on the Trident.
Fast attack and SSGN submarines go all over the world. They mainly do “interesting” stuff. They also go on WESTPACs, where they visit Japan, Australia etc. They often travel with a carrier battle group.
On Tridents we have a Crew Study and a Crew Lounge. Typically, the crew will watch a move together in the Crew Lounge after watch. The study has several computers. On my boat, four of them were used for playing computer games – mainly Unreal Tournament (1999 version…I served 1999 to 2003) – and three were used for people to study for various qualifications, mainly getting Qualified in Submarines.
One of the best aspects of submarine duty is the food. We still complain about it, of course. But on a submarine, there is no room to have a separate mess (kitchen) for officers, so enlisted and officers are served the same meal. The officers do eat in a separate area – the wardroom – but the meal is exactly the same. The cooks at the White House are supplied by the Navy, and usually at least one of the MSs (cooks) has worked there. On my boat, the Culinary Specialist Senior Chief had worked at the White House AND one of the Mess Specialist First Classes had as well. We mainly ate 10,000 varieties of chicken, but also shrimp, steak, lobster, etc.
