It has been more than a week since AirAsia Flight 8501 disappeared over the Java Sea, and the U.S. Navy has turned to an old standby to help find the main wreckage site: Tow Fish side-scan sonar.

Indonesia asked the Navy to send the USS Fort Worth, a littoral combat ship, to join the search on Saturday. Sailors with the Fort Worth began using the Tow Fish on Sunday from small 11-meter long rigid inflatable boats piloted by a mobile diving and salvage unit, Navy officials said. The Tow Fish, shaped like a torpedo, is designed to map the bottom of the ocean, which should help determine where wreckage from the airliner is.

The plane is believed to be southwest of Borneo under about 100 feet of water. Bodies of at least 37 of the 162 people on board have been found, and several sections of plane have been discovered.

The main fuselage has not yet been found, however. And that’s where the Tow Fish could come in handy. It looks like this:

Navy Diver 2nd Class Daniel Clarke, left, and Navy Diver 2nd Class Daniel Soulliard, right, both assigned to Mobile Diving and Salvage Unit 1, review a Tow Fish side scan sonar system aboard the littoral combat ship USS Fort Worth on Jan. 1. (Photo by MC1 Jay C. Pugh/ U.S. Navy)

In an interview released by the Navy, Diver Second Class Daniel Clarke said the sonar capabilities on the Tow Fish can find objects as small as a golf ball. It’s deployed off the back of the inflatable boats from a cable up to 300 feet long. The boats travel less than 10 mph while using the scanner, and review images on laptop computers.