A top scientist who pioneered China's record-breaking manned deep-sea submersible, the Jiaolong, hopes once again to boldly go where no man has gone before. But this time, Professor Cui Weicheng goes not in search of national glory, but of commercial enterprise. Cui, the first deputy chief designer of the Jiaolong, became a national hero in 2012 when the three-person vessel set a record by descending almost 7km into the Pacific Ocean. The descent gained China entry to an exclusive group of five nations capable of sending manned vessels below 3,500 metres and prompted state media to compare the venture to the nation's more glamorous space mission. So it came as a surprise to many when Cui left the Jiaolong project to join a little-known startup registered in Hong Kong with an ambitious goal - to build the world's first commercial deep-sea submersible fleet. But Cui is candid about his motivations for giving up his well-funded government job for the high-risk venture. "Profit," says Cui, with the enthusiasm one might expect had the Jiaolong just discovered a previously unknown deep sea creature. He is confident the private company can put together the talent and resources to build a fleet capable of reaching anywhere in the ocean. And he's equally sure there will be sufficient commercial demand. The fleet's first vessel, the Rainbow Fish, is scheduled to launch in 2019. Designed to reach depths of 11,000 metres, it will be able to visit the still unexplored deepest trenches of the oceans and dive deeper than any other vessel currently in use. Cui envisages that the vessel will eventually be part of a fleet containing a large mother-ship fitted with several ultra-deep landers (unmanned devices a little like underwater elevators that are tethered to the ship) as well as manned and unmanned submersibles. The landers will be used to study fixed spots while the submersibles will move about freely and be fitted with high definition cameras and robotic arms. All will be capable of reaching depths of 11km - equivalent to the deepest part of the oceans, the Challenger Deep in the Mariana Trench. Cui has already raised 300 million yuan (HK$379 million) for the project, mostly from private investors in Jiangsu - China's richest province, where businessmen are notorious for their prudence. He needs a further 200 million yuan and is looking for more investors, including those based in Hong Kong. While some may question whether the project more closely resembles science fiction than a sensible investment plan, Cui is sure he will strike gold. "When the Rainbow Fish is finished, we will rent the platform to the Chinese government. The demand for deep sea exploration equipment and services is strong, and growing," he says. "We will charge a reasonable fee which will generate a reasonable profit for our investors." In recent years China has adopted an aggressive strategy of scouting the sea bed for energy and mineral resources such as copper. The Jiaolong is already fully booked with assignments for Beijing and Cui projects that the cost of that project - less than 500 million yuan - will be recovered in "just a few years". Indeed, the Jiaolong's success provided a key incentive for Cui's departure from the project as he sought a new challenge. While the Jiaolong is for the exclusive use of the Chinese government, Cui plans to make the Rainbow Fish available to other countries, too. "The international demand will be considerable because no other platform can go as deeply as we do, and we can do a lot of things, from collecting biological samples to looking for missing airplanes," says Cui. He is also optimistic that his vessels and technology can attract customers with fat wallets, such as oil companies which are increasingly interested in exploring for resources at greater depths. Tourists could provide another source of fat wallets. Some foreign commercial companies have already started taking tourists down to the sea bed - although in relatively shallow waters - for sight seeing and for the thrill of experiencing an alien environment. "Many Chinese entrepreneurs are fond of adventures, and they can afford the tickets," notes Cui. With support from Shanghai's municipal government, Cui's company has established a research facility at Shanghai Ocean University to design and build Rainbow Fish. The Hadal Science and Technology Research Centre at SOU was named after the Hadal zone, a term used by scientists for the parts of ocean deeper than 6km. The centre will outsource the manufacture of critical components, such as hulls, from leading companies around the world. Though design and assembly will take place in China, engineers will use parts from the United States, Europe and Russia as well as China - much as the International Space Station was a worldwide collaboration. "It will be open to scientists around the globe so we can work together on some of the most intriguing and important issues to the human race," Cui says. When construction is complete, Rainbow Fish will be capable of studying such deep topics as whether life on Earth originated in the oceans' trenches - a belief increasingly held by the mainstream scientific community after the discovery of ancient microorganisms on the sea bed. "The sea trench is a paradise for strange, mysterious life forms. Some species could have stayed there and evolved for hundreds of millions of years without any contact with the world outside," says Cui. "If Chinese scientists are to make ground breaking discoveries, these are the last untapped zones on this planet." He says the company is in a race against time to finish construction by 2019 and to help protect the deep sea environment. "We must reach there and reveal the full picture of biodiversity in the ocean before the miners bring in their machines," he says. "Only with solid evidence can we argue with business and government for environmental protection in the deep. The Rainbow Fish is not built for the purpose of exploitation, but conservation." Professor Yin Jianqiang, a marine biologist with China Academy of Sciences' South China Sea Institute of Oceanology who recently discovered a new species of shrimp, says deep sea exploration is important because "we know basically nothing about what's down there". Manned or robotic submersibles have reached the bottom of the Mariana Trench only four times since the 1960s, with each journey limited to a small area with few samples. Yin accepts that such projects are capital intensive and there are no guarantees of profit. "It is unlikely that you will go down there and discover a gold mine. Scientific research usually does not generate sufficient, immediate profit to cover the cost, which can grow exponentially with the depth," he says. "The government should play a bigger role in such projects. They can afford it." The key question for investors is: will there be gold at the end of the Rainbow Fish?