At the southern edge of China's Guangdong province, facing the South China Sea, Shanwei's coastline stretches for 467.5 kilometers. It is the second longest in the province and the longest in eastern Guangdong. The city's maritime area measures 23,900 square kilometers, 4.5 times its land mass.
But the numbers alone do not explain why this stretch of coast has gained attention for the quality of its waters.
A latitude of advantages
Sitting at 22° north latitude, Shanwei lies along a band that circles the globe, passing through Hawaii, Miami, and Dubai. This position places it in a zone of interaction between tropical and subtropical air and sea systems.
The city has an average annual temperature of 23.2°C, with ample sunlight and rainfall throughout the year. Unlike higher-latitude waters, where winter slows biological activity, the subtropical sun here sustains photosynthesis by marine plankton year-round. Plankton form the base of the ocean food chain, converting solar energy into organic matter.
Field monitoring conducted by researchers from South China Normal University in the Honghai Bay area recorded a water temperature of 23.5°C and a pH of 7.8. Both fall within the ideal range for marine life.
Clean water by the numbers
Water quality along Shanwei's coastal areas has remained consistently high. Since 2021, the proportion of nearshore waters rated "good" or "excellent" has held at 100 percent, according to environmental monitoring data.
This is not solely a product of geography. The city has taken regulatory steps to protect its waters. One example is Pinqing Lake, a lagoon of about 23 square kilometers and the largest of its kind in mainland China. In recent years, local authorities enacted a specific regulation for the lake—the first of its kind for a single body of water in Guangdong.
Mangroves have also been restored along the coast. These trees act as natural filters, trapping pollutants and stabilizing shorelines. In Haifeng County alone, 417 hectares of mangroves were planted in 2025, with a survival rate of 92 percent. Species planted include Kandelia obovata, Avicennia marina, and Aegiceras corniculatum. According to local fisheries data, Shanwei's waters are home to more than 860 marine species across 14 categories.
Beyond the catch
The quality of Shanwei's coastal waters has also supported the development of new industries. The city is developing offshore aquaculture operations, marine ranching and tourism offerings such as island-hopping tours and sailing events.
For local authorities, the condition of the water has become a measure of broader environmental management. The approach, as one official put it, is to let the sea speak for itself.
Author | Feng Huiting
Photo | Shanwei Daily
