China's unmanned submersible Qianlong II has completed 50 dives since its commission, and will have a technology upgrade soon, scientists said.

The undersea vehicle, which is capable of diving to 4,500m, made its 50th dive on April 6 in the Indian Ocean, a part of China's 49th ocean expedition.

Of the 50 dives , 35 were in the Indian Ocean and 15 in the South China Sea, according to China Ocean Mineral Resources R&D Association.

In the southwest Indian Ocean alone, Qianlong II has traveled more than 2,000 km, they said.

The submersible, which first went underwater in 2015, is used for exploring deep-sea mineral resources.

"Its operations have become more stable after 50 dives," said Xu Chunhui, a scientist tasked with equipping the submersible.

Xu said a part of the upgrade will allow the submersible to work without the presence of its mother vessel. A new unmanned monitoring device will track the submersible, freeing the mother vessel for other activities.