Qualitatively, but not quantitatively.  A large metal object might not affect a conventional compass reading in a noticeable way, but if the enemy is flying around with cryocooled Josephson-junction magnetometers or whatever, they&#x27;ll still see a distortion in the local field.<p>I&#x27;d think that the permeability of a submarine hull -- magnetized or not -- would be very different from that of the surrounding seawater.