The theory that Archerfish's torpedoes exploited the joint between Shinano's waterline armor and anti-torpedo bulge may explain part of the damage. Rushed construction and compartments that had not been air-tested for leaks receive greater weight in this account. Four torpedo hits would impose severe structural and flooding loads even on a finished carrier. Shinano's unproven watertight system faced damage on a scale that left little margin for recovery.
Notable Point · 1:36:41-1:37:49
Rushed construction leaves Shinano's watertightness unproven
The armor-joint theory matters less than the combination of four torpedo hits and compartments that had never been properly leak-tested.