For nearly 400 years a legend persisted that Zhang's gold and silver sat at the bottom of the river.
In 2011, workers found many gold and silver items and coins while digging sand for construction purposes in the Jiangkou section of the Minjiang River, and the discovery enticed treasure hunters.
In 2016, police found that 10 gangs of illegal relics excavators and nine illegal relics-trading networks had sold artifacts from the site with a value of 300 million yuan.
This prompted archaeologists to undertake inland China's first underwater archaeological expedition, says Lu Haizi, an archaeologist with the Sichuan Provincial Cultural Relics and Archaeology Research Institute.