So, here's an anecdote of a sub that miraculously survived a head on collision. What's your point?
From the same article:
“The collision was so serious that the vessel was almost lost; accounts detail a desperate struggle for positive buoyancy to surface after the forward ballast tanks were ruptured.”
I doubt these are problems any submarine crew wants to deal with, even at slow speeds. Besides, one sharp edge at the sides will open her right up like a tin can.
I can't speak for the poster, but I would guess it's something along the lines of "military subs are pretty tough," and the bit about killing everyone onboard with a slow collision may have been an exaggeration.
They are meant for warfare and surviving torpedo concussions as much as possible, so depending on speed, a slow scrape with terrain might not be fatal.
Or it might be fatal. You don't know that. What we do know is the general construction of a sub, which is that of an "egg". It's built to withstand extreme global pressure (pressure from all sides at once, like water does). But as I'm sure you've noticed, eggs don't hold up very well against needles.
From the same article:
“The collision was so serious that the vessel was almost lost; accounts detail a desperate struggle for positive buoyancy to surface after the forward ballast tanks were ruptured.”
I doubt these are problems any submarine crew wants to deal with, even at slow speeds. Besides, one sharp edge at the sides will open her right up like a tin can.