Deep in landlocked Anhui province, eastern China, a 60-something farmer called Zhang Shengwu has drawn attention by launching himself into the water — and history.

Zhang, the inventor of Big Blackfish, a homemade submarine weighing over five tons and capable of diving to depths of eight meters, recently oversaw the submersible’s first successful trial in a river near to his Hanshan County home.

The trial was the result of over a decade’s worth of research and tinkering. Zhang described to local media how he had been fascinated by inventions since childhood, often working on small gadgets and tools in his spare time. Over the years, he acquired a variety of hands-on skills while working as a carpenter, welder, and a shipman.

But it wasn’t until 2014 that Zhang found a new spark of inspiration after watching a television program in which a man built a submarine from scratch. The idea gripped him, leading him to transform the sandy riverbank where he worked into his workshop and testing ground.

“I’ve been around water for years and have seen all kinds of boats — iron ones, wooden ones — but never one that could go underwater,” Zhang told state broadcaster China Central Television. “I thought, if others can build one, then so can I.”

Despite opposition from his family to the “expensive, risky, useless” idea, Zhang continued to devote himself to the experiment. Drawing on his carpentry and shipping experience, he began sketching out the submarine in his head. After buying basic materials — steel plates, batteries, and an engine — at a total cost of just 5,000 yuan ($698), in just six months he had built his first submarine: a 6-meter-long, 1.2-meter-high vessel weighing two tons.

On launch day, with sweaty palms on the controls, he recalled: “It felt like a dream. I was terrified it might leak, but I still wanted to go deeper.”

And while it did leak, Zhang was granted a national utility model patent for his design.

In 2016, he followed that project up with a surface boat, which also secured a utility model patent. “My mind is never idle,” Zhang said. “I’m always thinking about the design, and once I have an idea, I get to work.”

Next, Zhang invested 40,000 yuan into his second-generation submarine — what would later become Big Blackfish. He upgraded and extended the hull to seven meters, making it big enough to hold two people.

To boost stability, Zhang poured roughly two tons of concrete into the hull and installed two ballast tanks at the front and rear. “The tanks take in water to dive, and drain to float,” he explained. “The concrete acts as a counterweight to keep the submarine balanced.”

For better sealing, Zhang welded each joint and installed circular hatches. “I bought silicone to reinforce the seals, then glued over them with glass adhesive. Now it’s watertight.”

The vessel can reach a minimum speed of four knots, and Zhang is especially proud of its performance. “My propulsion setup is perfect for a sub,” he said. “One small battery and a motor can push this huge thing underwater. And it can dive for half an hour without a single drop of water getting in — it can even reverse.”

Looking ahead, Zhang says he hopes to build an even larger submarine. “You never know what you can achieve until you try,” he said.

Zhang is not the first civilian in China to dive into submarine-making. Several grassroots inventors have attempted similar feats over the past two decades. In 2009, Li Yuming, a self-taught “farmer inventor” who built five submarines, obtained a business license and became China’s first registered individual to operate in the submarine manufacturing industry.

In 2014, Zhang Junlin, a retired prison guard also from Anhui, developed a self-designed sightseeing submarine and performed a test dive in the South China Sea.

In recent years, the Chinese government has started cultivating rural talents, with a 2020 document outlining how it aims to have 1 million “innovation and entrepreneurship leaders” in countryside regions by 2025.

In Anhui, such individuals are eligible for a one-time start-up subsidy of 5,000 yuan if their business maintains stable operation for over six months. “Financial institutions and relevant funds will also be encouraged to support enterprises founded by these rural entrepreneurs,” the document states.

Editor: Tom Arnstein.

(Header image: Zhang Shengwu pilots his homemade submarine in Hanshan County, Anhui province, July 2, 2025. VCG）