China's manned deep-sea submersible, the Jiaolong, reached a depth of 6,965 meters below sea level Tuesday during its second dive into the Mariana Trench, surpassing a fresh national record set earlier in the day.

The vessel sat on the sea bed and started working at that depth.

This was the second time it sat on the sea bed for yesterday's dive. The previous one reached a depth of 6,908 meters, where sea drivers collected water samples and placed markers.

The dive, which began at 7 am after a leaking oil pipe in its hydraulic system had been repaired, is expected to re-check the hydraulic system and test various functions and the security of the submersible at great depths.

On Friday, the vessel reached 6,671 meters below sea level in the first dive, well surpassing the previous record of 5,188 meters made in July last year.

In the first dive, a malfunction was found in the submersible's No.1 communication system, but the No.2 set worked properly to guarantee the connection between the vessel and the Xiangyanghong 09, its mother ship.

The Jiaolong will attempt four more dives, aiming to move deeper to pursue the goal of reaching 7,000 meters below sea level between mid-June and early July.

The Xiangyanghong 09 reached the designated dive zone in the Mariana Trench on June 11.

"Both Shenzhou and Jiaolong are undoubtedly significant events in the history of China's science and technology," said Wang Zhonggui, deputy chief engineer of the manned space program. "As an engineer, I am keeping a close eye on their progress."

However, some more sober-minded netizens pointed out these achievements lag behind those of more advanced countries.