Windir, just activate R.E.M. - hydrophone mute for player fix (TDW compatible) on top of regular REM, if you want your hydro on surface.
Only works with hydro able to hear on surface of course (not rotative one).
http://www.subsim.com/radioroom/show...&postcount=130
Don't use the TDW ship inertia mod in your list, if you have it!
For some mysterious reason, it screw up the hydrophone hearing...for many users.
See how i put both REM in my list:
http://www.subsim.com/radioroom/show...20&postcount=1