Cossack 's first 18 - inch ( 460 mm ) torpedo struck the anti-torpedo bulge amidships , but failed to explode .
Torpedo had been fired too close to Glatton .
Cossack 's first 18 - inch ( 460 mm ) torpedo struck the anti-torpedo bulge amidships , but failed to explode because it had been fired too close to Glatton .