Haiyi-7000 glider during the scientific expedition (Image by SIACAS)

Chinese scientists broke multiple world records during a 54-day scientific expedition in the world's deepest sea trench and collected data for a sea trial of the country's first manned undersea vehicle.

The expedition in the Mariana Trench was completed on Tuesday and the team has returned to Sanya, South China's Hainan Province, the Xinhua News Agency reported.

Two of China's Haiyi ("sea wings") underwater gliders worked in water for 26 days and 20 days respectively, and sailed a total of 1,448 kilometers during the expedition, which made it the glider most frequently submerged in the world under 7,000 meters, Xinhua News Agency reported.

"Among the 102 gliding dives during the expedition, the gliders reached a depth of more than 7,000 meters 15 times as planned," Yu Jiancheng, a professor at the Shenyang Institute of Automation, Chinese Academy of Sciences, where the glider was developed, told the Global Times on Thursday.

According to Yu, Haiyi was designed to be capable of working consecutively for nearly a month at a depth of 7,000 meters.

The gliders reached a depth of 7,076 meters in the Mariana Trench, Xinhua reported.

The gliders continued to operate normally even when super typhoons Mangkhut and Kong-rey hit the area, and have collected valuable data as the typhoons passed over when all other scientific work had to be suspended, Yu said.

The gliders were also used in the Bering Sea area in July for the first time in an arctic expedition to measure the ocean's temperature, salinity and depth.

The team also conducted terrain detection at a 5,000-meter-deep seabed, and studied samples collected from sea floor sediments, which provide the basis for sea trial site selection of a manned underwater vehicle, Xinhua reported.

"It will be a breakthrough once the vehicle comes into use, which can help obtain first-hand hydrological data and largely increase the accuracy of hydrological investigations," Hu Zhiyong, chairman of the China Maritime Research Union, told the Global Times on Thursday.

The data can provide accurate information about ocean traffic, and can be used to predict ocean disasters and tides, Hu said.

The marine lander named Haijiao stayed in the trench and operated for 26 days, breaking a world record for one-time working hours in a dark environment, Xinhua reported.

The team also found a type of fish of Bassozetus at a depth of 7,012 meters, the deepest water area known to humans where such fish can survive.(Global Times)