For something that's pretty much indestructible, I'd say that's a fair tradeoff.
Nuclear submarines can, but that has nothing to do with being submarines and everything to do with being nuclear. Older diesel-electric submarines are usually slower than even the slowest surface vessels (aircraft carrier speed ~35 knots, top submarine speed ~25 knots) and can only stay underwater for a short amount of time. Since these subs are uh, coal-fired, it would be a bit weird to treat them as nuclear.
If you can't afford to shipping costs, build a ship to carry your sub around.
the issue is that it's impractical to even have a submarine. Even if you make a ship to carry your sub around you're going to need coal for that ship as well as the sub. I live on an island full of coal and it's expensive for me to move my sub around my docks, let alone anywhere else...



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