Chinese scientists say they have tested a monitoring device in the South China Sea that can improve detection of underwater currents believed to be a big danger to submarines. In a paper in the domestic peer-reviewed journal Earth Science Frontiers on Saturday, the researchers said the 1.4-tonne sensor could operate on the sea floor for weeks and surface in response to a signal from a mother ship. “[The sensors will gather] a large amount of on-site observational data urgently needed to further reveal the mechanism of internal solitary waves on the seabed,” Professor Jia Yonggang and colleagues with the Ocean University of China said in a paper. Chinese scientists say their model can predict dangerous ‘internal waves’ in Andaman Sea Underwater currents known as internal waves are a serious hazard in the South China Sea. They are caused when water of different densities passes over obstacles on the ocean floor such as a ridge, creating turbulence. Some waves can stretch over 100km (62 miles) long and rapidly drag submarines to crushing depths, according to various studies. In recent years, Chinese researchers found these powerful waves not only posed a direct threat to naval activities, but could also cause unexpected changes to the landscape below the surface, such as blocking channels or creating a sand dune out of nowhere. China has already built up one of the world’s largest ocean surveillance networks in the South China Sea, but floating buoys can be damaged. The new device could operate on the sea floor for weeks, detecting information sooner and at a greater range, the researchers said. Jia and the team said the data would help researchers create more accurate models to predict the formation, spread and strength of the internal waves across the waters. In the paper, the researchers said they conducted two field tests of the device in the South China Sea last year, dropping it on seabeds at depths of about 600 metres and 1,400 metres. A leak damaged one of the battery packs on the device but the team said they were still able to gather enough data. The main component of the device is an acoustic Doppler current profiler made by Teledyne RD Instruments, an American company that also supplies the same hardware to the US Navy. Teledyne Benthos, another US defence contractor, supplied the glass floats, according to the paper. Other components were sourced from Germany, Norway and Canada. The only made-in-China product noted in the paper is an underwater camera assembled at a laboratory in Xian, Shaanxi province. In April, more than 50 crew members died on board an Indonesian submarine during training in waters north of Bali. Though the incident is still under investigation, Indonesian Navy officials suggested the disaster could have been caused by internal waves. Satellite images showed such a wave in the area when the tragedy occurred. Meanwhile, the US military said last week that one of its nuclear submarines was damaged after hitting an “unknown object” in the South China Sea. The damage to the USS Connecticut forced it to surface and retreat to Guam. US authorities gave no details about the collision but some observers said the incident was highly unusual because the Seawolf-class attack submarine was equipped with state-of-the-art sensors and navigation instruments. A Beijing-based ocean scientist said China, the US and some other countries had placed a large number of surveillance devices in the South China Sea, but the chance that they collided with a submarine was extremely low because the waters were vast. “It could be a problem with their maps,” the scientist added. The Chinese government has demanded the US to release more details about the incident.