The anatomy of the DTIS camera system: the CTD (Conductivity, Temperature, Depth) records information about the temperature, depth, and salinity of the water DTIS passes through; the HPR transponder sends acoustic signals to the ship giving the position of DTIS; the altimeter measures how far DTIS is above the seabed, and the tail fin ensures that the unit moves in a consistent direction as it is towed by the ship. Credit: Dave Bowden