It hnk I was answering something else about sub communications rather then what you first said. The submarine is anywhere from fifty to several hundred meters deep. Not only that, but the vast majority of foreign submarines cruise at 5-8 knots to avoid detection. The only sub I know of that would regularly go significantly faster then that is the seawolf at 20 knots. The fact that you mentioned this tech in the first place implied that its the US developing it. And chances are if the tech can only actually detect a friendly submarine which we already knew was there, then it is next to useless. I fail to see how a submarine can possibly impact the surface of the water. Especially some of the slower ones out there.