How to sneak into a port

[LuftWolf]

Actually, in bottom limited environments other than Rock bottom, active sonar is quite limited.

Rock bottom shallow bottom limited environments seem to conduct sound just as well if not better than the top layer of a surface duct or CV, which both allow sound to propagate quite well and some distance. However, as I said, if you change the same situation with a bottom limited environment to Sand or Mud bottom, and the acoustic conditions change dramatically and the detection ranges are much shorter.