Have you ever wondered whatever happened to all of those ships and subs which were out at sea when the bombs fell?

The odds are good that a great many of them survived.

So... where did they go? Did they just stay out there wandering, did they come home to a wasteland, or did they just all give up and go to Tahiti or something?

Some of them probably ended up like this:

http://fallout.wikia.com/wiki/Wreck_of_the_FMS_Northern_Star

They would run out of fuel eventually. I am sure commercial ships carry just enough to get them to their destination, plus a reserve. Military ships typically travel with Oilers that fuel them along the way, but they still have a finite fuel supply.

Not sure where the technology was on nuclear powered ships, but I am sure there were some. Don't remember if the aircraft carrier in DC was nuclear or not, I think it was. In those cases, the limitations are food and other supplies for the most part.

So, eventually, they were all docked somewhere.

We also know the Sub the Shi were in crashed in San Francisco. There is also the Sub from Fallout 4 that had problems. There is the Valdez which was functional but taken out of use by the Enclave after the Great War.

As for Military Fleets of Ships. I would imagine they would have been tracked and even followed by enemies and thus targeted during the War. Subs on both sides during the Cold War carried nuclear tipped torpedoes.

Commercial ships like the Valdez and cruise ships would be all but extinct leading up to the Resource Wars. With everyone looking inward, international trade would be all but dead. Plus oil was all but out as well.

Any ship not destroyed would come home to highly irradiated ports. So they would run out of food and other resources soon enough. Even with nuclear subs, you need to resupply at some point. Nowhere to resupply the subs would be pointless at some point.

Yes, I suppose they must have docked eventually. There's bound to be a few ghost ships out there, though, just adrift.. no fuel, no crew.

I'm asking because there might be some mod potential in it.

Maybe a derelict vessel drifts by Boston, and you can go out to investigate?

Maybe a ship full of Chinese ghouls pulls into port and attacks?

Maybe a submarine washes ashore, still carrying a few "hot" missles ready to launch or explode?

Maybe a cruise ship shows up, promising to take passengers to a wonderful new place where everything is just peachy, but it turns out to be a scam?

There's already that Chinese Sub full of ghouls.

But that being said a giant cruise ship with the Fallout look to it full of feral ghouls would be pretty awesome to see. Maybe some of the crew survived and they go to land to raid every now and then, gathering supplies and new crew members, as in Feral ghouls.

Yeah, that's what I'm thinking. Why can't a tribe of raiders have their own big ship?

It would be very hard to keep it a float. It would require dry docking from time to time and fuel. There's also mother nature to deal with. Unable to detect hurricanes would be a serious issue. There's also creatures to deal with. How knows what's out there

I imagine most ships and submarines were destroyed or abandoned and began decaying. Some turned into settlements and supposedly some were outfitted with fusion reactors so some could still be operational. Supposedly Tenpenny and Moriarty both came from the U.K. from boat and we have the two Russian brothers and Cait in Fallout 4 so ship travel from Europe could be possible but is probably really dangerous.