Chinese experts arrived at a wrecking site in Thailand on July 7, with sonar equipment to acquire measured data of the shipwreck, according to Chinese newspaper Science and Technology Daily.

On July 5, two boats carrying a total of 127 Chinese tourists sank off the coast of Thailand’s Phuket Island. By the afternoon of July 8, the accident had caused 42 deaths with 14 people still missing. The information was confirmed by Chinese Embassy in Thailand.

Two Chinese professional rescue teams were sent to Thailand to assist with the salvage mission.

Senior engineer Gou Zhengkang was sent to the site, telling Science and Technology Daily that the deep water and short working time, as well as the long time of decompression, all placed challenges on the mission.

According to a video clip filmed by Thai rescue personnel, vital signs were spotted at 42 meters below sea level. However, a diver can only stay at that depth for 3 minutes and 27 seconds.

Chinese rescue teams applied sonar equipment and searched within a 500-meter radius of the shipwreck, said engineer Hu Juntao, who was sent to the site by the Second Institute of Oceanography (SIO), affiliated with China's State Oceanic Administration (CSOA).

“The sonar device is able to detect targets 1,500 meters below the water surface and send back the signals,” said Zhang Yifei, president of SIO’s engineering investigation institute. The primary task of the Chinese rescue teams is to detect the position of the ship and possible targets under the water, Zhang noted.

Zhang told Science and Technology Daily that compared with reservoirs, the sea poses a much more difficult rescue location, not to mention that the underwater target might move with water flows and waves, which adds increased difficulty to the mission.