The fact that sound travels quite well under water—and faster than it does through the air—was one of the reasons that sonar (SOund Navigation And Ranging) was developed as a submarine detection device. With it came the need for the Sonarman (SO) rating in 1943, along with several service ratings such as Sonarman Harbor Defense (SOMH).
But new audio technologies in the 1950s and 1960s such as moored underwater listening devices and towed sonar arrays led to the need for a new rating that would be tasked with operating and maintaining such devices. On November 26, 1969, the Secretary of Navy approved the establishment of the Ocean Systems Technician rating (OT). Originally designed as a general rating with its Sailors both operating and maintaining the sonar equipment at naval facilities, the increasingly complex nature of the equipment meant that, in 1982, two service ratings were established: Analyst and Maintainer.
One of the most advanced systems that Ocean System Technicians employed was the Integrated Undersea Surveillance System (IUSS). It was comprised of the Sound Surveillance System (SOSUS), Surveillance Towed Array System (SURTASS), and the Rapidly Deployable Surveillance System (RDSS). The data that OT Sailors collected through this system was collected, stored, and analyzed at Naval Ocean Processing Facilities at Dam Neck, Virginia (for data collected in the Atlantic) and Whidbey Island (Pacific Ocean data).
On October 1, 1998, Sailors serving as Ocean System Technicians were merged into the Sonar Technician rating.