Actually, Yamato was probably hit by TWO torpedoes fired by the USS Skate in 1943.
She didn’t “almost sink”, but did ship about 5000 tons of water as I recall, which was certainly unexpected given where the torpedoes struck (smack in the center where the torpedo “blisters” were located, along with the heaviest armor).
The problem turned out to lie in the quality of steel as well as in the system of cross-beams that connected the upper to the lower parts of the armor belts. The trusses were not up to the task, and were a compromise design due to resource limitations and time contraints. A patch work solution was effected, but only applied to the area struck by the torpedo(s). There was no ability, by 1943, to even think of a “retrofit” due to the strain the war was placing on Japan’s already meager war reserves of steel.
However, all this was really irrelevant once Japan lost the ability to protect its capital ships from the air.
As you’ll see if you read on towards the end of the website I linked above, Yamato was hit by over 20 (!!) torpedos off Okinawa, and no technology could have saved her from sinking.
She got hit by more torpedos than hit the ENTIRE “battleship row” at Pearl Harbor on 12/7/1941 ...
She also was on the receiving end of probably 30 bombs, whcih made a real mess on her decks, but the torpedos of course were what sent her to the bottom...the torpedo remains - to this day - the capital ship’s deadliest enemy ...