Low Flier, I believe the REMUS 6000 AUV fitted side-scan package consists of either:-
1. RESON Seabat 7125 Multi-Beam (200/400 kHz), or
2. Electronic Still Camera & Strobe, or
3. EdgeTech Dual Frequency (110/420 kHz) Side Scan Sonar and Sub-Bottom Profiler
In this case I suspect that the Seabat 7125 is being used, and is operating in the low resolution search mode at 200kHz. The location of a bottom debris field, no matter how dispersed, will enable a systematic backtrack to where the DFDR/CVR will be if torn from their mounts at impact. The location of larger items on the bottom will probably give other clues, like the heading on impact. The engines for example will be nearly straight down, but other items may have variable glide slopes.
The AUV will normally be programed to fly (it can not hover) at a predetermined height above the terrain at a speed commensurate with battery economy, e.g. 3 knots.
Woods Hole Oceanographic Institution have some
example imaging of a 14 foot boat with an outboard motor attached, which was located in 3,500 meters. The side-scan images are at 900kHz, and there is overlaid photographic imaging taken with the onboard strobe camera.
The search team have a TRITON deepsea ROV available to them to do any close-up examination and recovery.
Some of the more specific information you are requesting is not in the public domain, and time will probably reveal what was or wasn't done.
mm43