SCARABs, or "Submersible Crafts Assisting Repair and Burial" were small submarines that were initially built to plow and lay telecommunications cables under the ocean. However, during the 1970s, Bell Laboratories decided to rebuild the SCARABs into underwater robots—robots with a much greater range of tasks to perform.
SCARAB I and II were rebuilt at the Holmdel branch of Bell Laboratories from 1977 to 1981. They were deployed in different cable laying ships as their normal routine. However, the subs' moment in the sun—and the moment that prompted the making of this video, SCARAB: Proves Quality at Great Depths—was their use in search and recovery for the crash of Air India Flight 182.
The SCARAB subs in that effort were essential, since the crash had to have a thorough investigation, and all of the evidence lay under 6700 feet of water. However, the black box flight recorders were initially recovered by the SCARAB robots after 18 days, and the robots also provided some debris recovery assistance as well.
After that high-profile task, the SCARABS returned to their regular activities on various AT&T and other telecom cable ships, helping lay the first fiber optic cables that stretched around the globe. For more about the SCARAB's very first cable trenching assignment, see the film Voices from the Deep, from 1969.
An article from the Boston Globe circa 1985 lays out the submarines' capabilities and specs. These have, of course, since been surpassed by later generations of both SCARABs, Sea Plows, and Sea Tractors. As of 2010, some of the original SCARAB machines were still in use.
Footage Courtesy of AT&T Archives and History Center, Warren, NJ