senior hydrographer. >> they come in all shapes and sizes. side scan sonar, they all work on the same principle. they are going emit sound, that sound will emit the sea floor. it will receive it and interpret that in terms of an image or 3d data points on what's on the bottom of the ocean. >> twice the av has had difficult difficulties. can you describe the challenges? >> it's nice to get it nice and deep. you have to navigate the vehicle, you have to have controls. there is a lot of complicated interfacing to get this sonar down near the sea floor.