@iostrym Antitorps fire on any enemy torp that comes in range (and range is quite comfortable), when they are loaded. Even if those torps are fired to another target. So, yes, you can use destroyers to protect submarines, and submarines to protect destroyers. You can even put multiple naval units in the same spot. Like having 20 subs in the exact same spot. So they all protect each other. But in that case something with area of effect, can hurt all of them in the same time. Like Tempest torps/depth charges have aoe. Or battleships when groundfireing subs, etc. Notice also, that destroyer's antitorps have minimal range, under which they dont work. For example, if enemy sub is under your destroyer, then destros antitorp does not protect against that sub.
