side scan sonar and towfish works great
we currently use the hummingbird 997 and 1197 units for search/recovery. after trying multiple advanced imaging systems over the years, this is the most economocical and works wonderful. We have used it in murky lakes, rivers, creeks, ponds, and a sand pit with excellent results. The pictures are so clear that you can see the outline, and basically guide your diver directly to the victim if you have a underwater comm set ie; aga mask. We also have began using a towfish with the unit when the water depth is over 20ft. if you have any questions about this I would gladly discuss it with you.