I was pursuing a small convoy in October 1939 at night on the surface when I got spotted by a Black Swan Frigate. So before I dive, I line up a bow tube to shoot 1/2 meter under the Frigate, figuring that it's probably going to detonate well before the ship anyway, but it's worth a shot.
Rather than charge straight at me like the vanilla SH3 escorts are wont to do, this one starts zig-zagging as it closes the distance! Gotta love the improved AI...