China's unmanned submersible Qianlong No.2 completed its first exploration in the southwest Indian Ocean early this month, scientists said at a press conference on Wednesday.

The autonomous underwater vehicle (AUV) with a length of 3.5 meters, height of 1.3 meters, and width of 0.7 meters, was independently designed by Chinese scientists and can dive to a depth of 4,500 meters.

It dived 16 times during the exploration from Dec. 16, 2015 to March 4, 2016 in the southwest Indian Ocean. Its work covered 218 square kilometers with the maximum depth of over 3.2 km, said Liu Jian, chief designer of Qianlong No.2. Liu is also a researcher with the Shenyang Institute of Automation under the Chinese Academy of Sciences.

The AUV explored sea areas rich in sulfide deposits that contain various metals, detected deep-sea terrain as well as photographed sulfide, basalt and marine organisms, according to Liu.

"Though it has a weight of 1.5 tonnes, Qianlong No.2 can move vigorously in deep-sea water," Liu said.

Its work was done on undulating sea floor terrain but no crash occurred during the whole exploration thanks to the forward looking sonar technology, said Xu Chunhui, another researcher at the institute.

The success of the trial exploration of Qianlong No.2 in the Indian Ocean has proved that the AUV can be put into practice in deep-sea mineral resource investigation since it can adapt to the complex terrain in the ocean and finish underwater tasks smoothly, said Liu.

Qianlong No.2 will play an important role in the future development and utilization of China's deep-sea resources, Liu said.

The Qianlong No.2 has been under development since 2011. It was unveiled in October 2014.

Before the practical detection missions in the Indian Ocean, it had undergone lake trials and sea trials.(Xinhua)

Qianlong-2 unmanned submersible during exploration task. (Image by SIA)