there are a few generalisations in here....
having attended a few sub and UDT conferences over the last few years, I can say that the next generation of subs is very different from what we see today.
there are vast changes happening in how weapons will be carried and delivered.
there are vast changes happening in the way that subs can sense "red threats" - but correspondingly, that capability will also migrate to aviation platforms.
water is a denser medium to air - but the sound travels almost 4 times the distance further...
eg I have a recording of a "sounding charge" being picked up at 1500k's distance.