This week, ocean explorers mourned the loss of a legend in their field: Eugenie Clark, a marine biologist and authority on sharks.

"She was just one of those rare people that kept going until the day she disappeared," Fabien Cousteau told Live Science. "That's really the true definition of passion. There's very few out there that do that."

Clark died in Sarasota, Florida, Wednesday morning (Feb. 25) at age 92, National Geographic reported

Nicknamed the "Shark Lady," Clark began her career in the 1940s and was an early champion of the use of scuba diving for science. In addition to her daunting list of academic publications, she wrote popular books, detailing her adventures and obsessive love of fish, for the general public. (The first among them was "Lady with a Spear," published in 1953.) She dissected megamouth sharks and whale sharks. She studied poisonous fish in the South Seas for the Navy. She completed more than 70 dives to the deep sea in submersibles, including a series of descents in the 1980s that took her face-to-face with 14-foot-long (4 meters) sixgill sharks — and there's footage of it on YouTube. [8 Weird Facts About Sharks]

In the 14-minute video, Clark talks about retracing the steps of her personal hero, ocean explorer William Beebe.

In the 1930s, Beebe had made a series of record-setting dives in the deep waters off the coast of Bermuda in a cramped and crude submersible known as a bathysphere attached to a cable. His descriptions of the life he saw through his porthole were translated into lively animated drawings.

When Clark returned to Bermuda 50 years later, she had much more high-tech equipment — better cameras, better lighting and the comparatively roomy Pisces VI submersible. Her effort, called the Beebe project, was billed as the first study since Beebe's day that allowed marine biologists to observe the deep ocean of this region with their own eyes.

Clark and her collaborators settled on the dark seafloor some 2,000 feet (600 m) below the surface with a bunch of raw tuna to bait rarely seen sixgill sharks, or Hexanchus griseus, primitive cousins of their more common five-gilled sharks. And they were quite successful. Clark and photographer Emory Kristof recounted their experience in a 1986 article in National Geographic.

Cousteau, who is third in a line of ocean explorers starting with his grandfather Jacques Cousteau, first met Clark when he was a teenager. He said he was continually struck not just by her knowledge but also by her humility. 

"It kind of blew me away that someone of such a high caliber lived a fairly pious life," Cousteau told Live Science. "She was one of those silent forces."

In the footage from the Beebe project, a beaming Clark, then in her early 60s, looks into the camera after coming up from a dive and talks about how humbling it was to get to see even more life in the deep sea than Beebe did in the same place.

"As a child, William Beebe was my hero, and I used to read about him going down in the bathysphere, and I wanted to do that too," Clark says. "And I told my family, I said, 'I'd like to go down and be like William Beebe,' and they said, 'Well maybe you can take up typing and get to be the secretary of William Beebe or somebody like him.' And I said, 'I don't want to be anybody's secretary. I want to be like William Beebe going down.' And I can't believe it — here I am, doing just that in the same place. It's so fantastic."

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