Submarines continue to fascinate me, although I got just a tiny taste in 1972-73. I'm sure they've come a long, long way since then.
The first (Diesel) boat I was on had Mark 14 (ancient) torpedoes, Mark 37s and Mark 45s. The second had Mark 48s, which were brand-new in the fleet then, and SUBROC. The Mark 48 is all that's left, but in greatly-improved form.
https://en.wikipedia.org/wiki/Mark_48_torpdeo
In particular, I did not realize that the Mark 48 is powered by fuel that burns without oxygen, which has got to be a major savings in internal volume. Very cool.