Just to point out, Multibeam and Sidescan are 2 different things. Multibeam is genearally mounted to an AUV or WROV and tends to give a Hi-res image but a very small focal area. Sidescan is generally a 'towed fish' arrangement with a much wider swath but lower res. For this type of search a deepwater sidescan would be required with the fish flown at low alt above the sea floor behind a depressor weight for stability.