Scientific researchers wave aboard Xiangyanghong 09, carrier of China's manned deep-sea submersible Jiaolong, at its home port in Qingdao, East China's Shandong province, Feb 6, 2017. Jiaolong on Monday started a four-month scientific expedition to the northwest Indian Ocean, the Yap Trench and the Mariana Trench. [Photo/Xinhua]

On Monday, "Hailong 2", or Sea Dragon 2, and "Qianlong 1", both unmanned submersibles, were officially deployed at the National Deep Sea Center in Qingdao.

"Hailong 2", which needs a wire to link to the support ship, can work at a maximum depth of 3,500 meters. In 2009, the home-made underwater robot discovered a deep-sea hydrothermal "chimney" vent near the equator in the eastern Pacific.

Wireless "Qianlong 1" can operate at a depth of 6,000 meters.

The three types of subs are all domestically-made and each has its own specialties, according to researchers.

A new mother ship forJiaolongis estimated to be put into use in March 2019. It will be capable of carrying the three sub types together, said Yu Hongjun, director of the center.