You need water depth to make subs work best. But since the ships "sink", even if the rest of the CV disappears below the water line..a sub could do the same, and be just below the surface. Showing up when surfaced..a scope when submerged and scope up, and no vis on him when he is submerged scope down. Since aircraft only dropped depth charges on "just submerging" subs anyway...and since we have no indiviual control of the DDs, it doesnt matter anyway.
Certain planes could get a depth charge bomb option to load. And it could catch subs on the surface in transit, or on scopes if seen. Beyond that the origin of torpedo wakes could be used for an aim point. Basically it could be a slow pt boat, with much better armor, that has more torps, and can disappear "under" the sea after a few minutes of dive order.