A 60-year-old farmer's homemade submarine submerges in a local Chinese river, grabbing the spotlight throughout the nation.
Retired Farmer Builds Functioning Submarine in China
In a remarkable feat of DIY engineering, Zhang Shengwu, a retired farmer from Anhui province in China, has built a functioning submarine named "Big Black Fish." The submarine, capable of diving to 8 meters and staying underwater for about 30 minutes, is a testament to Zhang's years of hands-on experience in carpentry, welding, and shipping, as well as his persistent experimentation and practical problem-solving skills.
Zhang's journey began in 2014 when he was inspired by a TV program about submarine building. With an initial investment of 5,000 yuan, he started work on his first submarine. The initial model, however, had issues with watertightness, only submerging about a meter. Despite earning a national utility model patent for his design, Zhang was determined to improve.
Over six months, Zhang meticulously hand-constructed a steel vessel approximately 6-7 meters long. He welded joints carefully, installed circular hatches, and developed effective sealing techniques with silicone and adhesives. Every weld on the submarine was reinforced and sealed to improve watertightness. A five-meter pole with a waterproof camera allows Zhang to scan the riverbed before diving.
The maiden dive of the Big Black Fish took place in the Fengle River, and the video of the event was shared on Douyin, China's TikTok equivalent. The clip quickly spread across Chinese social media, showcasing Zhang's impressive achievement.
The Big Black Fish is designed for two passengers and can cruise at 4 knots. It uses two ballast tanks to control buoyancy and two tons of concrete in the hull to maintain stability. The cockpit features a blue-lit instrument panel, and an external joystick wrapped in anti-slip rubber is present for easy maneuverability.
Zhang's fascination with boats began in childhood, growing up near the Yangtze River basin. He invested 40,000 yuan into his second-generation model, completed in mid-2025. The submarine is capable of diving to 8 meters (26 feet). During testing, the waterproof camera system helped Zhang recover a fisherman's lost net, earning him a 3,000 yuan reward.
Zhang's project is a notable example of grassroots innovation fueled by practical skill, perseverance, and learning by doing rather than formal engineering education. His story serves as an inspiration for those who dare to dream and are willing to put in the hard work to make those dreams a reality.
Technology played a significant role in Zhang's submarine construction, as he relied on resources like TV programs and videos to learn the basics of submarine building. Moreover, the use of modern materials such as steel, silicone, and adhesives, along with innovative techniques like welding and sealing, was essential in creating a functioning submarine.
