Chinese oceanographic research ship "Xiang Yang Hong 18" has returned to Qingdao after overseeing record-setting dives in the Mariana Trench by Chinese-developed underwater gliders, reports China Central Television.

中央电视台报道，中国海洋科考船“向阳红18”见证国产水下滑翔机在马里亚纳海沟破纪录深潜后已返回青岛港。

The "Haiyan" gliders have undergone a series of standard tests.

As part of the six-days of dives, the "Haiyan" gliders are said to have broken the record for a deep-sea dive, hitting a depth of 8,213 meters.

The previous record is said to have been around 6,000 meters.

"It is a historic step in China's deep-sea observation. The successful development of the deep-sea underwater gliders will guide and stimulate the advancement of China's unmanned deep-sea research equipment," said Wu Lixin, director of the Qingdao National Laboratory for Marine Science and Technology.

Gliders, unlike other unmanned vessels, dive and rise through a shift in the ballast of the vessel, allowing the craft to gain or lose depth in a 'yaw,' or see-saw type descent or ascent.