Chinese farmer builds 5-tonne submarine by hand

Zhang Shengwu, a Chinese farmer in his sixties, has stunned the internet after successfully launching a homemade submarine — a 5-tonne vessel he built almost entirely by hand.

The vessel, named Big Black Fish, recently completed a successful trial dive, reaching a depth of 8 meters.

Its builder, Zhang, is a farmer from Zhangdu village, Yuncao township, Hanshan county, Ma'anshan city, east China's Anhui Province. He is a self-taught inventor who has enjoyed making homemade inventions in his spare time since he was young.

Photo shows the first submarine built by Zhang Shengwu, a Chinese farmer who has a keen interest in homemade inventions. (Photo/CCTV News)

He used to work as a carpenter and welder, and also worked in shipping.

Over 20 years ago, Zhang returned to his hometown to build a sand and gravel wharf, and has worked there since.

Watching cargo ships come and go every day, he always felt something was missing, Zhang recalled.

His idea of building a submarine took shape in 2014 after he watched a television program featuring a self-made submarine.

"I've seen metal boats and wooden boats all my life, but never one that could go underwater," he recalled. "If others can do it, why can't I?"

With years of experience in carpentry and shipping, Zhang put his knowledge into practice.

After conceiving a blueprint, he spent around 5,000 yuan ($696.58) on steel plates, batteries, and an engine to build his first submarine—a 6-meter-long, 1.2-meter-tall, 2-tonne vessel.

Photo shows the main structure of a 5-tonne, 8-meter-deep diving submarine built by Zhang Shengwu, a Chinese farmer who has a keen interest in homemade inventions. (Photo/CCTV News)

During its maiden voyage, Zhang admitted he was both nervous and thrilled. "It felt like a dream. I was afraid of water leakage but hoped it could dive deeper," he said.

Although the prototype earned him a utility model patent, it had leakage issues during submersion. But rather than give up, Zhang saw it as a beginning.

In 2016, he designed a surface craft that also won a national utility model patent.

"I feel like my mind never really takes a break — I'm always thinking about new designs. As soon as I come up with something, I start tinkering. Like this boat — its standout feature is that it barely makes any waves when it moves," Zhang explained.

Not satisfied with just small-scale success, Zhang went on to invest more than 40,000 yuan to build a second, larger and more advanced submarine—the Big Black Fish.

The upgraded vessel stretches 7 meters in length and 1.8 meters in height, and features a cockpit that can accommodate two people.

Zhang Shengwu, a Chinese farmer who has a keen interest in homemade inventions, pilots his self-built submarine. (Photo/CCTV News)

For improved stability and buoyancy control, Zhang added around 2 tonnes of concrete ballast and designed four ballast tanks to manage diving and surfacing. He used silicon and glass sealants to ensure watertight construction, reinforcing all weld points for durability.

The result: a 5-tonne submarine with a displacement of around 7 tonnes, capable of diving 8 meters and cruising at a minimum speed of 4 nautical miles per hour.

"The way of propulsion I've adopted is actually pretty well-suited for a submarine. Just a small battery and an electric motor can push this big vessel underwater. It can dive for half an hour without leaking a drop — and it even runs in reverse," Zhang proudly noted.

For Zhang, the journey has been about far more than engineering—it's about enjoyment and fulfillment.

Now, he's setting his sights on building an even larger, more capable submarine. "Only by trying and realizing what's in your mind can you truly discover what you're capable of achieving," he said.

Zhang also hopes that by creating bigger submarines he will inspire children to embrace innovation and develop a stronger sense of national defense.