The advent of miniature unmanned submarines known as remotely-operated vehicles (ROVs) and sophisticated “side-scan” sonar have allowed underwater adventurers to locate some of the world’s most celebrated wrecks, from the Titanic and the Bismarck to ancient Roman and Phoenician vessels.

The new technology has transformed the field, which was once severely limited by the difficulty of sending divers or manned submarines to extreme depths, and the hit-or-miss nature of combing thousands of square miles of seabed for sunken ships.

Both academic and commercial missions now feel confident of making discoveries almost every time they put to sea, given reasonable information on the position of a ship when it went down.

Bob Ballard, the celebrated underwater explorer who found the Titanic and the Bismarck, is even planning an expedition to Antarctica to track down the wreck of Sir Ernest Shackleton’s ship, HMS Endeavour.

The search begins on a computer, using software that brings together information about the target ship’s last movements to highlight likely locations on the seabed. Side-scan sonar and magnetometers are then to survey large swaths of the ocean floor, picking out sunken structures that are likely to be wrecks. ROVs are then launched and steered towards any objects of interest, using sonar, high-powered lighting and video cameras to make closer investigations. The more sophisticated ROVs also carry force-feedback manipulators — mechanical hands that can grab objects under the control of an operator on the surface.

Odyssey Marine Exploration searched more than 1,500 sq miles of ocean for the wreck of the Republic, with 1,000 sq miles surveyed in the past two years alone. The survey identified 24 target sites that were inspected using ROVs.

Measurements of one of the wrecks, taken with side-scan sonar, match the length and sidewheel of the Republic. A video inspection has confirmed the wreck’s identity.

The company is now planning to excavate the site using some of the most sophisticated maritime archaeological equipment yet assembled.

The expedition will be mounted from the Odyssey Explorer, a 80m survey ship that can carry a crew of 42 people for 60 days at a time. It is fitted with an array of cranes and A-frames for lowering ROVs and sonar probes.

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