Why Titanic changed thinking about ship subdivision

Which accident had the most significant effect on naval architecture?

Titanic, because it sharpened attention to longitudinal as well as transverse subdivision inside ships.

Asked for the most consequential accident in naval architecture, The answer chooses Titanic rather than HMS Captain. Its reason is the effect on thinking about subdivision. Transverse divisions alone could not answer every flooding path; designers also had to consider how protection extended longitudinally through the hull. It treats that lesson as important to warships as well as merchant ships.