Tsinghua University and Peking University, two of China's most prestigious academic institutions, have condemned the sale of water from their campus lakes and rivers as an illegal profit-making scheme, after controversy erupted over its online sale by individual sellers.

During China's national college entrance exam, which lasted from June 7 to 10, bottled water labeled as "Peking University's Weiming Lake Water" and "Tsinghua University's Campus River Water" appeared on the secondhand goods platform Xianyu, attracting "quite a few" buyers, according to one seller.

The water was sold for 99 RMB (approximately $13.8) per 500ml, with sellers boasting it could "boost brainpower" and "enhance intelligence".

On Friday, staff from both universities told Xinhua News Agency that water from campus rivers and lakes is a valuable resource for maintaining a healthy ecosystem and should not be commercialized for profit. Such actions are firmly opposed.

Both universities have contacted the platform to request the removal of these products and encouraged people to report similar incidents.

Zhu Wei, an associate professor at China University of Political Science and Law, told China Youth Daily that sellers were exploiting people's anxieties about academic success.

Another law expert warned that marketing claims such as "boosting intelligence" and "enhancing brainpower" are blatant hype and could constitute false advertising, urging consumers to remain rational, according to Xinhua.