ABOARD XIANGYANGHONG 09, Jan. 30-- A female pilot trainee of deep-sea manned submersible operated Jiaolong on Thursday for the first time in the southwestern Indian Ocean.

"When the sub started to come up at 3:30 p.m., I asked Zhang (Yi) to pilot Jiaolong according to the training schedule and she did it very well." said Tang Jialing, a pilot of Jiaolong.

Zhang operated engines of the sub and managed to drain off some water in the ballast tank with its hydraulic system, according to Tang.

"I practiced all these steps in the testing pool but it is very meaningful for me to have such practical experiences in ocean," said the 27-year-old pilot trainee.

"I also learned from Tang that I must pay attention to every detail during the operation, or the sub might be put into danger," she said.

Although the sea conditions were bad and the sub rocked wildly when it came up to the sea surface, Zhang piloted the sub calmly and steadily, according to Tang.

China recruited six pilot trainees of deep-sea manned sub out of 130 candidates in 2013. Zhang is the first trainee who has piloted Jiaolong in ocean.

All six pilot trainees took their first practical training by watching pilots' operation in the last voyage and they will pilot the sub under guidance after three trainings in ocean.

Jiaolong, China's first deep-sea submersible, collected rocks of 9.5 kg, chimney vent of 0.9 kg and sulfide of 0.5 kg in a hydrothermal area.

Reaching its deepest depth of 7,062 meters in the Pacific's Mariana Trench in June 2012, Jiaolong is on a four-month expedition in the southwestern Indian Ocean.