Has anyone tried this tactic before...

I was near English port in shallow waters and everything was buzzing with destroyers.
After sneaking for many hours I sank one freighter that was docked.
Soon after that 3 destroyers were approaching at my location, I was in 30m shallow water and I knew I was dead.
So I tried something just for fun, I headed at flank speed to the sunken freighter (his bow side was still above the water) and I hide there...near him
at about 20m deep. I even ram him couple of times but with no damage to my sub. I was waiting for the destroyers to see if
they can drop DC on me but they could not do that. All they did was just circling around and they drop some DC but not even close to me...and some even stopped and waited. So I went to a periscope depth and shot 3 destroyers that were around me very close and I eventually managed to escape 2 more.
So I don't know what to call this tactic but with a little bit of luck it works in shallow waters near ports.
What do you think is this realistic in SH3? or is it more like cheating?
(my english is not perfect)