Overview
- Zhang Shengwu, a 60-year-old from Anhui province, spent roughly ten years building the “Big Black Fish,” a homemade sub about seven meters long and around five tonnes.
- Reports describe a two-person vessel powered by batteries and an electric motor with ballast tanks and about two tonnes of concrete, rated for short dives to roughly eight meters and around 30 minutes underwater at up to about four knots.
- After an early 2016 prototype leaked, Zhang launched the current version to a nearby river in 2025, according to Clarín, with footage and local reports highlighting short trial dives.
- Cost accounts differ across outlets: some cite an initial 5,000 yuan (about US$700) outlay, while Clarín reports a later additional spend of about 40,000 yuan on a larger steel structure and ballast.
- Coverage on Chinese platforms and in international media has surged, as unnamed experts quoted in reports warn of pressure hazards, lack of certification and unverified performance claims.