During the initial dives that found the fdr memory, the lead diver indicated that the seafloor was covered by a layer of mud of at least 80centimeters. Later 1 meter was mentioned. So they need to have both a clear mapping and a ground/mud penetration capability for that. Does anyone here know what kind of side scan/ multi beam system has that capability, or if there are underwater ground penetration radar systems for such soft toplayers?
If they are not successful this way they might end up having to remove the toplayer. There is some technology development in that field, but... Normal dredging methodologies seem a bit 'rough' for this purpose.