Okay, following my previous core question, after the apocalypse, one of my sets of survivors in this setting, the Usnay, managed to live in a fleet of ships for over a thousand years.
This is probably less of a direct question, and rather me making sure I have all my ducks in row here on the thoughts behind their survival, to ensure I'm not missing anything critical, and to have a bit of a reality check, I suppose.
Here are the facts:
They are living as a fleet of ships that are relics of the mid 21st century (2060). There are probably around sixty to eighty vessels total.
This includes their escort: three prototype navy destroyers that protect the civilian fleet from threats. These destroyers were state of the art at the time, with onboard cold fusion reactors, some form of magnetised armour plating, probably a deck mounted railgun or two, flak point defence, and stores of missiles and supercavitating (hypervelocity) torpedoes. In other words, enough to murder the crap out of anything looking at you funny.
The oldest of these destroyers is effectively the government centre and the flagship since it combines defence, order and early warning. Navigation orders come from the flagship as it analyses its records of the seas and uses its instruments to determine the best routes that avoid the roughest seas and disasters waiting to happen.
We can assume the first captain of this fleet was a pretty awesome person. After all, as the world broke down from nuclear war, they went around rescuing ships and coastal populations, and they planned for living on the sea for quite a while from the start.
They have converted a couple of Oil Tankers into Hydroponic or Aeroponic Farms (probably converting various tanks into rotary hydroponic facilities). I'm a little concerned about the engineering required in this conversion but hopefully its feasible. Given the kind of crops that grow best hydroponically, their main diet will be beans, tomatoes, cucumbers, strawberries, and leaf lettuces. Sounds like a decent salad! This is supplemented by fishing (at least some of the fleet will be fishing trawlers). Going by the figures in this question and assuming the absolute worst case scenarios, we can assume our two hydroponics tankers can support a fleet population of at least 10,000 people or so.
Many places actively catch rainwater with various devices and filter implements, but a couple of vessels may also be specialised in waste treatement and desalination. The fleet tends to stick to rainy climes where possible. Some processing of waste occurs where possible to save fresh water, but it is otherwise dumped into the sea.
Some vessels may bolt and tether to one another where this is convienient and appropriate; unbolting again if a storm is approaching. There are also freight barges that ship stuff and people between the various other vessels.
A converted Aircraft Carrier has effectively become a huge apartment block. Parts of planes were probably cannibalised to make structural components for homes here. This wasn't likely straight away, but rather after the long quiet set in and population density began to rise a bit. The aircraft carrier can also be assumed to be relatively new, probably also with its own fusion reactor. Its possible that its planes were actually drones if airforce development went/continued that way; though I doubt the successor to the F22/F35 was phased out instantly. Its also possible that a cruise ship or two are part of the fleet as alternate accomodations.
They have 'magic' for maintainence. This is, as noted in previous topics, the ability to interface with ambient nanomachines. We can assume that most generic rust and wear to the hulls can be fixed by nanomachines assuming they have access to some new materials occasionally.
Some trips to land are possible during this time; but are dangerous due to the demons that now inhabit the land. Since the demons have unpredictable abilities, engagement with them is on a purely last-resort basis for a ground crew (those few demons that might attempt to swim/fly out to the fleet would be annihilated by the destroyers, but coastal support for landers may be more difficult). Nevertheless, obtaining metal scrap and rare earths (and in earlier trips for the first century; canned foods), is possibily worthwhile enough to warrant it.
I guess my main questions here are:
A) How long would this conversion take? I'm assuming a couple of generations? This question has some good ideas about design (semi-submersibles, rafted components) but my plan assumes that is not possible to access any large manufacturing facilities for any significant length of time, and the skilled labour to use such facilities may be rare as well.
B) Given the available nano-maintainence, I assume the ships will be fine for this period (if rusty in all non-essential sections to preserve resources). Alot of the central crux of this plan assumes that most of the tech will last and last for a very long time. This topic's main answer says that the hulls will last many generations. But how long will modern ordnance stay live and usable? What about the computers? I'm also assuming that our Fusion reactors are Deuterium => Tritium and that we can indefinately sustain them using some process to extract it (2H) from seawater.
C) How would people evolve during this time (both physically and socially)? I know a couple thousand years isn't enough for drastic changes, but I'm assuming that people will become favoured towards being darker skinned. They will also steadily lose the concept of personal space. I have them currently on a loose pseudo-military hierarchy/meritocracy with the Sea-Marshal as the leader.
D) And of course, anything else I might have missed!
Other possible reference topics looked at include: Would it be possible for a city floating on water to exist? and What would be the ramifications of someone who has lived their entire life at sea?