In a workshop tucked against the South China Sea, Zhou Hao machines parts with precision down to 0.003 millimeters — about one-thirtieth the width of a human hair. For the 46-year-old chief technician at the Chinese Academy of Sciences'Institute of Deep-sea Science and Engineering, that margin separates success from catastrophe 10,000 meters beneath the ocean's surface.

"When machining parts and debugging equipment, not a single step can be done carelessly," Zhou said.

He has solved 366 technical problems in the development of deep-sea research equipment over the past decade, according to the institute. He has overseen 316 upgrades for sea trials, helping China's domestically built submersibles achieve multiple domestic and international firsts.

Zhou worked on both the Shen Hai Yong Shi and Fen Dou Zhe manned submersibles, witnessing China's deep-sea technology leap from operational to world-leading depths.

The pressure at 10,000 meters beneath the waters reaches nearly 1,100 kilograms per square centimeter — similar to a small car pressing on a fingernail. "If a car breaks down on the road, you can wait for help. But at 10,000 meters deep, a small mistake can put both the equipment and people in grave danger," Zhou said.