Government divers pushed one of China's dive records during an experiment in the South China Sea yesterday, going 50 per cent deeper than its last record set eight months ago.
Six divers with the Shanghai Salvage Company, a subsidiary of the Ministry of Transport, descended to the target depth of more than 300 metres in a pressurised metal sphere that they then left to explore the sea floor about 250 kilometres southeast of Hong Kong for more than three hours, according to Xinhua.
The water pressure at that depth is about 30 times that at the surface. A sudden return to atmospheric pressure would cause inert gas to bubble in their blood and block blood vessels, causing a painful and fatal condition known as the bends.
Saturation diving technology allows divers to live and rest in pressurized quarters onboard the mother ship, thus avoiding repeated decompression procedures and prolonging their dive time for missions to days, weeks or even months.
The last record, 198 metres, was set by the same team in May.
Wang Zhenliang , the director of rescue and salvage at the transport ministry, told Xinhua they were now aiming for dives at 500 metres, though he wouldn't speculate when that would be achieved.
Shen Hao , another company director, said the divers involved in yesterday's mission would return to their onboard living chambers to undergo gradual decompression, which would be completed by Friday.
China's impressive advances in deep diving still lag behind other countries. Saturation dive technology was invented in the US in 1938. In 1988, the French commercial deep sea diving company Comex set the offshore diving record at 534 metres.
China has signalled its determination to catch up with other countries in the race to explore the deep ocean, noted a marine researcher at the State Oceanic Administration's Second Institute of Oceanography, who did not want to be named.
"The race in deep sea is similar to the space race," he said. "We entered decades late, but we want to catch up in a decade."