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.

That risk drove Zhou's relentless rigor. He consistently spends more than 10 hours daily in the workshop, debugging equipment before sea trials, repeating tests two to three times. His path was neither easy nor expected.

Zhou graduated from technical school in 1999 and took a fitter job at a mining machinery company in Northeast China's Liaoning province. "I decided to become the best fitter in the industry," he said. He practiced filing — a basic skill — tens of thousands of times, wearing out nearly a thousand files.

Within a few years, he had mastered lathes, milling machines, boring machines, planers, grinders and welders.

In 2016, seeking new challenges, Zhou moved to Hainan province and joined the Institute of Deep-sea Science and Engineering. "I thought it would be a great honor if I could use my skills to help build a strong maritime nation," he said. But he quickly learned that land-based machinery and deep-sea equipment differ in nearly every detail. Still, his approach never changed: rigorous, repetitive, and relentless.

Zhou has earned the title "Great Country Craftsman of the Year" and received China's top labor honors, including the National Model Worker award and the China Skills Award. He leads a national demonstration model worker and craftsman innovation studio, and receives a special allowance from the State Council.

Zhou's seasickness is legendary among colleagues.

"I vomit even when drinking water at sea," he said. During one mission to the Mariana Trench, he said he vomited for the first seven days until his stomach cramped and his legs went weak. "But when the equipment fails, I pull myself together and solve the problem."

Zhou is now training the next generation. Four of his apprentices come from local technical schools in Hainan. One is a senior technician, two are technicians, and one, born after 2000, is an advanced-level technician.

"I always tell them not to treat this as simple tasks to check off," Zhou said. "They must embrace the responsibility of contributing to the nation's high-level deep-sea technology."

His innovation studio operates under a simple motto: "There is no road in the deep sea. We don't need to follow — we are the path."

Zhou said, "The scientific research spirit is about going all out and never giving up."

As China pushes its deep-sea ambitions, Zhou believes craftsmanship will determine how far the country can go. "Passing the torch, sustaining craftsmanship — that will nurture more great country craftsmen," he said.