Abstract: A system for deploying sonar for surveying in deep water includes a submerged movable platform deployed in the deep water at a depth below a thermocline and surface wave action, a propulsion mechanism for moving the platform through the water in a controlled manner, and a multibeam echosounder attached to the platform, wherein the echosounder includes a Mills Cross transmitter and receiver array. A method for deploying sonar for surveying in deep water comprises deploying a submerged movable platform in the deep water at a depth below a thermocline and surface wave action, employing a propulsion mechanism for moving the platform through the water in a controlled manner, and employing a multibeam echosounder attached to the platform, wherein the multibeam echosounder comprises a Mills Cross transmitter and receiver array.