I have to agree with
@Icywinter and be blunt with you Abject: that is an incredibly unrealistic, dare I say stupid, idea. Don't get me wrong: I love U-505. I want to read kancolle fics with U-505. But I'm not going to try and shove her into a story where she doesn't belong.
U-505 is not seaworthy, nobody knows how to make her seaworthy, none of the modern submarine equipment in use by the US Navy would fit on the comparatively tiny Type IXC hull, and it'd be far easier to train crews for modern attack boats than a submarine not even the remaining WWII vets would know how to operate.
First off, I am not attempting to shove anyone into a story where they don't belong. I was merely asking questions and speculating on things. Secondly, in regards to what
@Icywinter had said, there's no guarantee that the US even has any modern day attack subs left in this story. We know that the US Navy, as well as all of the worlds navies for that matter, had losses in the early part of the war before ship girls began appearing. What we do not know is exactly how many ships the US navy has lost to Abyssals thus far. We also don't know just how many ships were lost in the opening rounds of the war when humanity didn't even know about the existence of the Abyssals, let alone anything about them.
An earlier chapter in the story, The First Thirty-Six, which was a flashback had the US lose 4 supercarriers in three hours. Now as anyone here would know, US carriers are never by themselves. Thus this implies one of two things: A) the escorts of t hose supercarriers were either wiped out or reduced to the point where they could no longer protect said supercarriers; or B) The Abyssals managed to strike down the supercarriers despite their escorts. The same chapter also has
Captain Goto noting that the Abyssal ships barely showed up on radar. Who is to say that the same wouldn't be true for sonar as well. Also in that chapter it was shown that Harpoon missiles and five-guns from Goto's guided missile destroyers didn't really do much of anything against the Abyssal pre-dreadnoughts. With that information in mind, one has to wonder just how long it took the US to figure out that modern naval warfare doctrinaire wasn't going to work against the Abyssals. How many US surface ships and subs do you think had the belief that they could spot anything with their radar/sonar systems long before it could threaten them? How many of those ships do you think were sunk because they held that belief? How long do you think it took the US to figure out that anything relying on modern day guidance systems are going to have a hard time hitting their target? We even see this much in the reworked version of Chapter 44: Splash One when the bunker busters were dropped on Northern Princess. Out of 24 bunker buster bombs which had both laser and GPS guidance systems, only one managed to hit the abyssal princess which was big enough to make battleships look like destroyers. At that point of time humans knew about 'abyssal spookiness' and yet the bombs still missed. Think what any ship back in the early part of the war would have fared.
In addition that, the same chapter also mentions that the China seas had seen the worst shipping losses in decades over the course of three months. Now while it's unknown for the moment if the same was true for everywhere else or not; but it wouldn't be unreasonable to think that if the Abyssals weren't sinking a lot ships elsewhere at that time then they were making observations. It has been shown in the very few times in the story where we see things from the perspective of the Abyssals that they're not dumb. They're able to think on a tactical level. There is nothing thus far that shows that Abyssals are not capable of thinking on a strategic level. As such, in the unknown amount of time that passed before their existence became known to humanity, the Abyssals might have been making observations on the movements of naval ships. Even if the Abyssals weren't making observations, they would still have the advantage of virtually not showing up on radar and possibly sonar as well. The human ships on the other hand would likely show up clearly on the Abyssals radar/sonar. Even if many Abyssal ships don't have either sonar or radar systems, those that had either or both could easily direct the others. With these things considered, to becomes rather easy to see that there's a high chance that the US lost a lot of their attack subs, if not all of them. Since it takes a rather long time to build just one ship of any kind; the idea of reactivating old ships would become a lot more attractive, even if it only just so that you have something protecting the coasts while newer ships are being build.
Thirdly, it's possible to make an unseaworthy vessel seaworthy again. Your statement about nobody knowing how to make something like U-505 seaworthy again is false. As U-505 was captured and towed rather than sunk after being captured, the documents on board the submarine were thus available for study and translation. As the ship itself was studied by Navy intelligence and engineering officers in 1945, it reasonable to assume that any information needed to restore the submarine to working order exists. Also, you do not need anybody from the second world war to train a crew how to operate the submarine because the manuals which were on board U-505 are likely still around, either in their original or translated forms. Information about the interior components for the submarine would also likely still exist even today, not only in the US but in Germany as well. This stems from the fact the German manufacturers who had made U-505 interior components were able to supply them to the museum when they had requested them back in 1954. Considering the fact that the internet seems to be quite alive and well within this story, it wouldn't be a far stretch to think that any information which didn't have could be sent to them. You are correct that none of the modern day submarine equipment in use by the US Navy today would fit on U-505. But considering how well modern technology fairs against Abyssals, perhaps that would actually be an advantage. Besides, the key word I had used was the would
probably out fit some modern tech, not
definitely.
.
EDIT:
That would be prohibitively difficult.
The answer may well be "actually quite a lot." We'd have started the war with about 70-75 nuclear submarines. Even the ballistic missile submarines are torpedo-capable.
The Abyssals probably COULD hunt them down by committing ASW-specialist Abyssal destroyers and other, lighter ships... But then, doing so would probably be as hard or harder than hunting down the IJN subgirls, because the levelling effect would translate USN nuclear submarines as having evasive qualities anywhere from "good" to "excellent." And it doesn't seem like the Abyssals have been concentrating all that hard on ASW, as demonstrated by how well the Japanese lewdmarines have been able to perform as scouts.
I actually wouldn't be surprised if the US submarine force is one of the main reasons the Abyssals haven't been able to overrun the Atlantic with surface vessels in the opening months of the war. The RN shipgirls are obviously a major factor there too, but it seems like they're kept fairly busy close to home. Though I may be mis-remembering some of Skywalker's Eurobotes content..
It would also explain why the Abyssals are concentrating submarines in the Atlantic. Because while in theory US submarines ought to be pretty good at hunting and killing other submarines, the levelling effect would tend to work against that because there was literally ONE sub-on-sub kill in the entire Second World War.
It may very well be the case. The leveling effect could also explain why lewdmarines are able to act as scouts. Not to say that a regular sub couldn't do so as well, but it might be more difficult for them. Though it's still unclear just how much of the US submarine force is left by this point in the story. It doesn't help, as I've mentioned earlier, that modern day guidance systems don't really work all that well on Abyssals considering that the torpedoes used by the Navy today all have some form of passive/active guidance system. So it wouldn't be unreasonable to think that some subs were lost before that was realized. But so far we only know for certain that laser and GPS guidance systems don't really work on Abyssals as well as not really showing up on radar. Though what I find interesting is that in the chapter "Because that's totally logical..." that Mo's UAV gave every other ship in the fleet washed-out garbage but gave
her a clear image..
And speaking of the Mighty Mo, we really haven't seen her since the last time she appeared and I honestly would love to see more of her.
