China's manned deep-sea submersible, the Jiaolong, kicked off its fifth test dive eight hours ago at the northeast Pacific Ocean. In its first four attempts, the submersible has reached a new record depth of 5,188 meters. It is on its way returning to the surface.

During the Jiaolong's earlier missions, the crew took photos and video, surveyed seabed, and took samples from the ocean floor. The purpose of the test dives is to conduct scientific research and test the vessel's different functions. Deep-sea diving poses a challenge to vessels' capacity to withstand water pressure. The crew must work underwater for six to eight hours at a time.

By reaching depths of 5,000 meters, the Jiaolong is now capable of exploring more than 70 percent of the world's seabeds. These test dives pave the way for a record-breaking 7,000-meter test dive attempt in 2012.

Japan is the current world record holder, with its Shinkai submersible reaching 6,527 meters in August, 1989.

China, initiated the Jiaolong project in 2002. China is the fifth country to send people more than 3,500 meters below sea level, following the United States, France, Russia and Japan.

The Jiaolong is named after a mythical sea dragon. It passed its first major benchmark between May and July last year, with 17 dives in the South China Sea, reaching depths of over 37-hundred meters.