Three weeks after Malaysia Airlines Flight 370 went missing, Pete LeHardy and his crew were on a plane headed for Australia.

Previous teams searching for Flight 370 had come up fruitless, but the general consensus — at the time, at least — was that the plane was buried underwater some 500 to 1,000 miles off the southwest coast of Perth.

LeHardy, a business development manager at Louisiana-based Phoenix International, had a simple mission: Find the wreckage.

Over the next 70 days, he and his team employed an automatic underwater vehicle (AUV) named Artemis, also known as the Bluefin-21, to search more than 850 square kilometers throughout the area. They found nothing.

"It wasn't just us. There were 26 nations out there searching as well," LeHardy says. "And we all agreed: This just wasn't the spot."

Malaysian officials recently announced they would begin searching a new area in early August, hundreds of miles south of the original location. Until then, Artemis is sitting in storage in Australia.

"Even though we didn't find anything, we still accumulated a lot of data about that part of the ocean that we didn't have before," LeHardy says. "The ocean is so vast in that part of the world. But now we at least know a little more about what's down there."

AUVs like Artemis — drones, essentially, that operate remotely at great depths — aren't exactly new. But until recently, they haven't been used much, restricted largely to commercial research for oil and gas industries.

However, as they continue to become more common, assembled and used by universities and ocean exploration organizations, the vehicles are being employed for all new tasks: searching for wreckage, researching new depths and helping us paint a clearer picture of what's under the surface.

Less than 5% of the world's oceans have been explored at depth. Paul Bunje, Ph.D., senior director of prize development and ocean health at the XPRIZE Foundation, an educational nonprofit based in Culver City, California, points to an imbalanced budget ratio between NASA and the National Oceanic and Atmosphere Association (NOAA).

"In 2013, NASA's exploration budget was roughly $3.8 billion — 150 times greater than NOAA's budget of $23.7 million," he says. "We have better information about the surface of Mars than we do about the depths of our oceans."

It all comes down to priorities. Public funding for the sciences hasn't been high in recent years, Bunje says, and interest in ocean exploration has been sinking (no pun intended.)

To make matters worse: In May, an AUV named Nereus, owned and operated by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, imploded six miles under the Pacific.

What happened exactly isn't clear, but scientists speculate the pressure at that depth — about 16,000 pounds per square inch — caused the robot to cave in.

Nereus was 30 days into a 40-day expedition to explore the Kermadec Trench, northeast of New Zealand — the second deepest trench in the world. It was scheduled for six more exploratory expeditions later in the year, all of which team members say will have to be scrapped.

The WHOI did not respond to multiple requests for comment.

"What happened to Nereus is a shame," LeHardy says. "There are so few of these machines out there, and when one gets destroyed like this, it makes a huge impact on everyone involved."

Artemis operates using basic sonar. Unlike Nereus' mission to explore, LeHardy's team usually embarks on assignments to find aircraft, like Flight 370, that have sunk underwater. The vehicle sends sound waves to get an estimate of how deep the area they're exploring is; then, once it has an idea, it plunges as deep as possible and photographs the terrain.

It's part of the reason why LeHardy still feels optimistic after the failed search off the coast of Perth. Although they didn't accomplish their main goal, they still collected pictures of a previously unknown part of the ocean — baby steps toward eventually mapping most of it. With the next search coming up in August, they'll collect more data just like it.

"The ocean really is our final frontier," Bunje says. "If we map as much terrain as possible, we illuminate the unknown. And there are always radical breakthroughs in the unknown."

It's not necessarily about searching for sunken treasure or lost cities, he says — it's just about knowing what's down there.

Learn more about how AUVs are being used on NOAA's website.