60-year-old farmer builds submarine by hand

To improve its stability, Zhang poured about 2 tons of concrete into the bottom of the submarine and added two ballast tanks at both ends. "There are two ballast tanks, water fills the tanks to dive, and drains to the surface. The concrete provides weight to maintain stability," he explained. He also reinforced all weld points and used silicone and adhesive for watertight sealing.

Watching his submarines grow larger and his techniques improve, he dreams of building an even larger, fully functional one. "Only when you try and succeed, you do realize what you're truly capable of," Zhang said.