Zhang Wuyi, 38, who made headlines last year by manufacturing personal submarines, recently unveiled his first unmanned submarine in Wuhan, Hubei province.

While Zhang was at the controls in the operating room near a big swimming pool, the submarine floated, submerged and moved slowly forward and backward.

After his colleagues put some sea cucumbers in the pool, the submarine's underwater camera started to track the targets, collecting about 10 of them within 20 minutes using its robot arms.

"It's like an automatically controlled undersea harvesting machine, and absorbs aquatic products like a vacuum cleaner," says Zhang, who started to make a submarine on his own in 2009 because he's interested in it and he sees a potential market.

In October 2011, he sold his first submarine to the operator of a sea cucumber plant in Dalian, Liaoning province, for 150,000 yuan ($24,000). The undersea boat, which can dive up to 30 meters deep, can catch sea cucumbers for 10 hours continuously.

Since then, Zhang and his coworkers have been upgrading his submarines at his company in Wuhan.

The latest model weighs 4 tons and is 4.5 meters long and 1.6 meters tall. It can dive up to about 50 meters deep. The unmanned sub can operate without any safety risk for a human operator, he says.

It has four "legs" so that it can walk slowly underwater on the bottom. The camera, lighting system, robot arms and the positioning system allow it to fish for marine creatures accurately.

For fishermen at sea, the work is highly intense and hazardous, he says, and the production rate is lower than it would be for well-developed robot submarines.

"Such submarines can replace manual fishing, for fishermen's benefits," he says.

The submarine is custom-built for an aquatic products company in Yantai, Shandong province, with a deposit of 60,000 yuan. Zhang will take it to Yantai this week for a trial voyage in the sea.

After his work with personal manned submarines was widely reported last spring, he says a government department official came to him and expressed concerns about safety.

"No one can shoulder the responsibility if an accident happens to the person who's under water," he says.

So he canceled all three orders he had last year and concentrated on developing unmanned submarines.

He has already invested more than 3 million yuan in the project - some from his own pocket, some borrowed from friends and some from investors.

He says money has been his biggest challenge.

"Our team has more than a dozen people," says his colleague Yu Laijiang, from Ningbo, Zhejiang province, who joined Zhang several years ago. "Although we weren't able to pay salaries on time for several months, few of us left because we're confident about the promise of the program."

"I appreciate Zhang's perseverance for his dream, so I try my best to help him," says another colleague, Chen Yiruo, a retired engineer from a boat company.

Zhang, meanwhile, says he will unveil a new product in May: a vessel that can be used both at sea and on land.

Contact the writers through xulin@chinadaily.com.cn.

(China Daily 04/09/2013 page20)