In the weeks after Malaysia Airlines Flight 370 vanished, most likely in the Indian Ocean, Australian officials said they knew less about the area they were exploring than is known about the surface of the moon.

It's actually even worse than that.

Surveys of Mars and Venus are considered around 250 times more accurate than existing maps of the underwater region where Flight 370 searchers are looking—a lightless, virtually lifeless seabed.

There, the contours of the ocean floor have only been approximated by bouncing satellite radar off the surface of the sea, or by taking low-resolution sonar soundings from boats that passed through the area a generation ago. Research indicates the presence of dramatic vistas, including a volcanic plateau and mountains roughly the height of the Swiss Alps. There is so little bacteria that scientists believe a whale carcass would take decades to decompose down there.

Sources: Australian government; NOAA

The hunt for Flight 370 has been overshadowed in recent days by the Malaysia Airlines jet shot down in Ukraine, but it remains one of the greatest mysteries in aviation history. Unlike the Ukraine tragedy, which left tons of debris, not even a stray suitcase has been found from Flight 370, which disappeared en route from Kuala Lumpur to Beijing on March 8 with 239 passengers on board, leaving little more than a trail of cryptic satellite transmissions behind as it diverted off course.

Investigators have used those digital handshakes between the plane and an Inmarsat PLC telecommunications satellite to identify an area the size of West Virginia where they think the plane crashed in the water after it ran out of fuel. But an initial effort to probe the depths in a different area using a submersible drone called Bluefin-21 found nothing.

“ It used to be that when a ship sank in the deep sea, we would commit the ship and souls for eternity to the deep—gone forever ... That's not true anymore. ” —David Gallo, Woods Hole Oceanographic Institution

Now, two months after pausing its search, the Australian Transport Safety Bureau is ready to reboot the massive probe. It is poised to select among bids from the world's most-advanced deep-water specialists, including offshore oil-and-gas companies, maritime research institutions and treasure hunters eager to use their technologies and experience to solve the Flight 370 riddle—and potentially raise their own profiles in the process. The ATSB is expected to choose one or more of the bidders over the next several weeks before relaunching the search with $56 million in funding in late August. Those costs will be split, in amounts still to be determined, between the Australian and Malaysian governments.

The good news is that the world's deep-sea recovery industry is now more sophisticated than ever, thanks to offshore research by oil-and-gas firms that have gone progressively deeper, as well as militaries and insurance firms. Technologies developed to hunt for everything from the Titanic to lost parts of the Space Shuttle Challenger have further expanded frontiers, allowing investigators to work as deep as about 3.7 miles, or slightly more than the deepest-known area of the Flight 370 search zone.

"It used to be that when a ship sank in the deep sea, we would commit the ship and souls for eternity to the deep—gone forever," said David Gallo, director of special projects at Woods Hole Oceanographic Institution, the Massachusetts-based research outfit that helped find Air France Flight 447, which disappeared in the mid-Atlantic Ocean in 2009, and is bidding to participate in the Flight 370 hunt. "That's not true anymore."

David Gallo, director of special projects at Woods Hole Oceanographic Institution, observed a test on the REMUS 6000 autonomous underwater search vehicle in Woods Hole, Mass. Dominick Reuter for The Wall Street Journal

But with no hard evidence of where the plane went down, the search will test the recovery industry's abilities like nothing before. In June, Australian authorities shifted the search zone for a third time—by about 600 miles to the southwest—after reanalyzing satellite transmissions. Even then, they said it was impossible to know whether the fresh search area would prove correct.

At stake is the emotional well-being of relatives and friends of the passengers from the plane, left in suspended animation while authorities search for answers. There is also the issue of maintaining public trust in the aviation industry, which rarely experiences unsolved disasters.

For its part, Australia has such a visible role because the waters are in a region it handles under a global civil aviation agreement. Under the bidding process, companies angling to play a role in the search can work alone or bid as part of a consortium. Each signed nondisclosure agreements about their bids with the Australian government, but The Wall Street Journal was able to confirm through people familiar with the process at least eight outfits that are bidding for a role.

Among them: Fugro FUR.AE +0.85% Fugro N.V. Netherlands: Amsterdam €15.94 +0.14 +0.85% Volume (Delayed 15m) : 2.02M P/E Ratio N/A Market Cap €1.34 Billion Dividend Yield 9.32% Rev. per Employee €194,027 12/10/14 U.S. Stocks Tumble Along With ... 12/09/14 European Stocks Plunge 11/24/14 Search for Malaysia Airlines F... More quote details and news » FUR.AE in Your Value Your Change Short position NV, a Dutch oil-and-gas consulting firm that has brought its top subsea sonar guru out of retirement to help with the effort. Others include Oceaneering International Inc., OII -3.56% Oceaneering International Inc. U.S.: NYSE $53.62 -1.98 -3.56% Volume (Delayed 15m) : 449,810 P/E Ratio 13.80 Market Cap $5.84 Billion Dividend Yield 2.02% Rev. per Employee $297,991 More quote details and news » OII in Your Value Your Change Short position a Houston oil-services firm that makes space suits and robotically controlled amusement park rides that also helped find the Titanic in 1985.

Then there are the treasure hunters—companies and individuals that make a living exploring the deep for profit. One is Odyssey Marine Explorations Inc., a Florida firm listed on the Nasdaq that a few years ago recovered around $500 million from a Spanish ship sunk off Portugal in 1804.

Tom Dettweiler, director of mineral exploration at Odyssey Marine Exploration. Lexey Swall for The Wall Street Journal David Mearns of Blue Water Recoveries at his office in Midhurst, West Sussex, England. Jude Edginton for The Wall Street Journal Colleen Keller at the San Diego regional office of Metron Inc. Sandy Huffaker for The Wall Street Journal

Others include Williamson & Associates, a Seattle outfit led partly by Art Wright, a well-known underwater explorer who still rows competitively in his 70s. Another is Blue Water Recoveries, a U.K. firm led by bearded oceanographer David Mearns which holds the Guinness World Record for the deepest wreck ever discovered: a German World War II blockade runner known as Rio Grande found in 1996 nearly 18,900 feet below the surface.

"It is definitely the search of my generation," said Colleen Keller, a senior analyst at Metron Inc., a Virginia-based scientific consulting firm that also has joined a consortium competing for the Flight 370 contract. Her firm assisted with the Air France search and has also worked with the U.S. Department of Homeland Security.

Efforts to reclaim lost vessels from the depths go back hundreds of years. In 1834, the British warship Royal George was partially salvaged using diving helmets with breathing apparatuses based on a design originally improvised from an old suit of armor and a fire hose.

In the 1930s, a mission was proposed to recover valuables from the torpedoed ocean liner Lusitania using a 200-foot stairwell sealed in an iron tube. While the tube itself was built, the money to search the ship—lying more than 305 feet underwater—ran out. Since then, many divers and documentary crews have reached the wreckage.

Searchers went far deeper in the 1960s and '70s, when searching equipment improved and military emergencies pushed engineers to stretch their technologies.

In 1966, the U.S. Navy lost a hydrogen bomb in the Mediterranean after a midair collision between a B-52 bomber and refueling plane. Afraid the bomb would fall into the wrong hands, the Navy sought help from Woods Hole scientists who were experimenting with a miniature submarine called Alvin—one of the world's first deep-sea submersible vehicles. It located the bomb at a depth of about 2,900 feet.

A few years later, the U.S. Navy spent two years searching for a missing film cache that had fallen back to earth from a spy satellite. This time, it used a manned submarine developed in-house to recover the film from nearly 16,400 feet deep.

Deep-sea searchers soon realized sonar devices, rather than the human eye, allowed for large areas to be quickly assessed for debris, or underwater mines that threatened submarines. Especially useful was side-scan sonar, a technology developed by the U.S. Navy and at research institutes including the Scripps Institution of Oceanography and the Massachusetts Institute of Technology in the 1950s.

Side-scan sonar works by sending high-powered pulses laterally into the water from a device usually about 150 feet off the seafloor. The pulses hit objects—rocks, debris, mountains, valley walls—and bounce back toward the device, where they are received and integrated into an image that displays a shadow of what is on the bottom of the ocean.

By the 1980s these devices were widely available and robust enough to endure the pressure of deep waters. Treasure hunters, meanwhile, were experimenting with new methods to take cameras and sonar devices deeper.

Ships consigned to oblivion for decades or even centuries were discovered, including the Titanic. It was found in 1985 using a device developed by Woods Hole called the Argo, a towed sled equipped with cameras and strobe lights which fed data back to a ship on a long cable.

Similar sled vehicles fitted with side-scan sonar were used by Williamson & Associates in 1988 to locate the wreck of the SS Central America, or "Ship of Gold," which sank off the coast of the Carolinas during a hurricane in 1857 with up to $760 million in gold at today's prices. It caused such a loss to U.S. banks that it helped spark one of the first global financial crises—the Panic of 1857. A diving firm funded by a consortium recently recovered nearly 1,000 ounces of gold, but the ship may still have some 16 tons remaining.

The technologies also found a market stamping out shipping-insurance swindles. In one case in 1990, a company later acquired by Oceaneering International searched for a cargo ship called the Lucona after it was blown up by an Austrian businessman who later changed his identity with plastic surgery. When he was eventually caught, he goaded investigators to find the missing ship and prove he was guilty—which they did, in waters some 14,100 feet deep.

Yet the challenge of locating missing jet aircraft can be far more difficult.

Malaysia Airlines Flight 370 is likely resting on the floor of one of the least mapped sections of the ocean, according to officials. Searchers hope the missing plane didn't end up on one known feature called the Broken Ridge. Jason Bellini reports.

When a plane strikes the water, even in a gentle belly glide, only a few large pieces of debris tend to stay intact. The engines—and their virtually indestructible turbines—snap off and sink to the bottom. Sometimes the cockpit will survive the impact. Much of the rest of the plane usually disintegrates.

On a flat, featureless sea floor, these large pieces of debris send back strong images, known as "hard targets," to a sonar device. But they can easily become camouflaged in rock fields or ravines.

The earlier hunt for Air France Flight 447 illustrates the complexities. Investigators found debris on the ocean surface, giving them a relatively good idea of where the plane went down. But the subsequent search, with contributions from Woods Hole, Metron and Mr. Mearns of Blue Water Recoveries, took two more years.

Searchers ruled out areas near the plane's last communicated location after an undersea pinger locator failed to detect emergency beacon signals there. Instead they relied on complex drift models that tracked movements of debris and bodies found floating on the Atlantic Ocean to determine a probable final location of the plane.

Arguments over the models—which proved wrong—delayed the search for the plane. It eventually was found in the same zone where the pinger locator had originally searched.

With Flight 370, investigators don't have the benefit of debris or precise final coordinates to give them a starting point. Moreover, the patch of sea they have identified as the plane's most likely resting place is one of the least-understood places in the world, 1,100 miles off Western Australia.

The only sonar surveys of the underwater topography were taken by boats that passed through the area mainly in the 1960s and 1970s, including a Soviet research vessel called Vityaz that now is a floating museum in Kaliningrad. A core sample of nearby seabed taken by a different Soviet vessel found compact yellow mud made from millions of years of accumulated plankton exoskeletons. Carbon dating showed that it took 1,000 years for less than a fifth of an inch of new mud to settle.

Authorities are doing additional mapping of the area with three modern sonar survey ships, including one contracted from Fugro NV. But their equipment operates from the surface, and the images are unlikely to be sharp enough to spot plane debris, instead revealing the lay of the land for the next group of searchers being brought in under the fresh tender.

To find the plane, those searchers will have to use undersea sonar equipment, including side-scan sonars, that can be sent to within 150 feet of the seabed.

Coordinating the search tender from a drab office block in the Australian capital of Canberra is the ATSB, and its chief commissioner, Martin Dolan, a longtime public servant who previously ran Australia's workers' compensation program. Helping him sift through search bids is a panel of five senior bureaucrats, including a former BP PLC ocean-fleet manager and an ATSB marine engineer.

The decision will ultimately be Mr. Dolan's, and the bidding rules allow him to consider more than merely the lowest bidder. There will be some tough choices, which could be crucial in determining whether contractors fulfill their mission of finding the plane. Among the hardest: whether to bet heavily on companies like Williamson & Associates, which specializes in using relatively simple towed sonars, or outfits like Woods Hole that have their own higher-tech autonomous underwater vehicles, or AUVs. A wrong choice could reduce the search's odds of success.

The Ocean Explorer 6000 towed sonar vehicle. Oceaneering

Towed sonars are attractive because they can cover large areas relatively quickly—an important advantage given that ATSB officials are giving bidders just 300 days to explore the 20,000-square-mile search area due to intense public interest.

But they are also sometimes hard to manipulate. Searching for the AHS Centaur, a World War II-era hospital ship, in 2009, scientists had to tow a sonar device with more than 4 miles of cable through a ravine 295 feet wide. They likened it to the movie "Star Wars," when fighters flew through a narrow trench at high speeds to unload a final shot to destroy the fictional Death Star. One device snapped off its cable and was lost.

The AUVs, by contrast, can be programmed to navigate finicky terrain. But AUVs cover less ground because their batteries can't power energy-intensive sonars, and they cannot be operated in rough seas as they have to be hauled back on deck each day, placing a ship's crew at risk.

They also can go haywire. Woods Hole's flagship deep-sea AUV, the Nereus, imploded under high pressure off the coast of New Zealand in May. Another multimillion-dollar AUV, the Remus 6000, failed to resurface on a recent research trip. "The decision, fortunately or unfortunately, in the end rests with me," said Mr. Dolan.

A Remus 6000 autonomous underwater vehicle being used in the search for Air France Flight 447. Mike Purcell/Woods Hole Oceanographic Institution

Most of the firms that spoke with The Wall Street Journal said they were bidding as part of consortia, as very few have the equipment, ships and expertise to carry out the massive search alone. A number have already descended upon Canberra to make their cases, including Mr. Wright of Williamson & Associates, who along with Mr. Mearns of Blue Water Recoveries worked earlier with Australian officials to locate a torpedoed World War II Australian warship. Ms. Keller of Metron said she would relocate to Canberra to operate a data center crunching sonar images from search ships and updating authorities, if her firm wins the bid.

Once the search is finished, if the whole seabed ends up being mapped, the area will be the most comprehensively interrogated strip of ocean in the world, Mr. Dolan of the ATSB said. Scientists will know every boulder and divot that dots its surface. Whether that includes Flight 370 remains to be seen.