Blade attack

[Berinhardt]

I got a little overconfident at periscope depth the other day, and while I was busy lining up a shot on a distant target, this escort sneaks up on me and starts his run right over the top of me. He had me cold, and I had no way out. In my panic to move, I retracted the periscope, went to flank speed and hit the "S" key instead of the "C" key causing my boat to surface. Except that at 40 feet, my periscope blades cut him to ribbons, he burst into flames and then sunk a few minutes later.

I know that this has been a known "feature" of the game (using blades at shallow depth to take out destroyers), but is anyone using it as a regular tactic?

Does it work on things other than DD's - for example, if I have a wounded merchant moving slowly and I don't want to surface to finish him off, can I set my depth to 70-80 feet and rip hull?

How about subchasers and sampans?