An oceanographic ship carrying China's manned deep-sea submersible, the Jiaolong, left eastern port city of Jiangyin Sunday for the Mariana Trench to attempt the world's deepest manned submersible dive.

The submersible, named after a mythical sea dragon, will go 7,000 meters under the surface of the Pacific Ocean between mid-June and early July, according to the voyage's plan.

Three oceanauts,Ye Cong, Fu Wentao and Tang Jialing, will pilot the Jiaolong and will be supported by nearly 100 scientists aboard who test the submersible's functionality, conduct scientific research and take seabed samples during the dive.

Haiyang-6, a Chinese research vessel, had carried out specific surveys in Mariana Trench earlier this year to figure out the maritime environment for the Jiaolong.

The Jiaolong is the world's first manned submersible designed to reach depths of 7,000 meters below sea level.

It completed 17 dives in the South China Sea from May to July in 2010, with the deepest reaching 3,759 meters, which made China the fifth country, following the United States, France, Russia and Japan, to send a manned dive over 3,500 meters below sea level.

The submersible succeeded in diving 5,188 meters below sea level in the Pacific Ocean last summer, enabling China to conduct scientific surveys in 70 percent of the world's seabed areas.

Success in going the depth of 7,000 meters will mean it is able to reach almost all of the world's seabed areas.

"The scientific expedition of the Jiaolong is aimed at benefiting the mankind. The deep sea where few people visit has amazing resources waiting to be discovered, such as hydrothermal sulfide and manganese nodules," said Ye Cong, 32, key driver of vehicle.

China will promote the development of deep-sea technologies and equipment, including comprehensive research ships, mothership of manned undersea grafts, and deep-sea autonomous underwater vehicles, according to Liu Cigui, head of the State Oceanic Administration (SOA).

China initiated the Jiaolong project in 2002. The vessel is expected to return to China in mid-July.