I remember sinking a carrier with one eel...
and here's the kicker.
It was by accident
Long story short: I was doing the quick mission where you have to sink the yamato in the task force, well, I had her all lined up and fired all tubes at her.
a minute went by and I checked the scope again and I saw the yamato, still dead centre of the scope, then from the right came a carrier, can't remember the class, but it was a fair size, and it went right into the line of my torpedoes.
I blinked and saw one fish strike her clean amidships. She blew up. That's how I can describe it. Just "KABOOM-BOOM-BOOM-BOOM" fighters flying from the deck, showers of spakrs, flames erupting everywhere, the boilers exploding.
All with one torp. She went down pretty quickly too...
I can't remember which version this was, probably 1.1 or stock, cause it was fairly early after it being released.
But it was one amazing fluke.