Six pilot trainees for the Chinese deep-sea manned submersible "Jiaolong" have completed their first dive in the southwest Indian Ocean.

The Chinese submersible conducted dives on Sunday and Monday near hydrothermal sulfide vents on the ocean floor. Two female pilot trainees, Zhao Chengya and Liu Xiaohui, operated Jiaolong during the dive.

Ding Zhongjun is the deputy commander of Jiaolong's 35th expedition.

"This sea area is quite challenging to them, as the sea bed environment is much more complicated, which requires them to respond quickly. They performed well during the dive and completed their mission. Jiaolong faces high-grade and urgent requirement from our country, especially from scientists involved in deep sea researches. So more and more diving missions are waiting for us."

Trainees need to act as co-pilots and pilots for three dives respectively before becoming qualified pilots.

Jiaolong, which is named after a mythical dragon in Chinese legend, reached a record depth of over seven thousand meters in a test dive in the Pacific's Mariana Trench in June 2012.