i personally try to go under the ship with a magnetic, helps fix any weird angles, but i think it depends on what ship you're going after and if you want to be "authentic" or not.
on regards to the type of ship, destroyers should be shallow and deep for anyone else.
as for authenticity, my sh3 is stock so the torpedoes navigate just as well at any depth, while in real life torpedoes running very shallow are very suspect to the movement of the waves.
the... uh... depth of the ship? oh darn i've forgotten the term... draft? can be found in the ship recognition manual.
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