sorry Pontius Navigator
devices are made in differing types and can descend below the surface or some types stay on the surface
both can set to listen at different depths etc etc
so a 4000m cable you suggest ? - of course a surface sonar would not hear it
also re wreckage the OP was responding to my original post where i stated
If the MH370 had crashed in that region then any floating small wreckage will be soon reaching the shores of Western Australia due the prevailing weather and sea conditions
seems you may not been reading the whole thread either
Last edited by rog747; 5th Apr 2014 at 16:47.