For about two months, this phenomenon has appeared intermittently in Da Bac, Tran Van Thoi, and Khanh Hung communes. The distinct line between the two water colors runs parallel to the coastline, stretching for tens of kilometers.

Seawater displaying two colors, blue and reddish-brown, in the coastal area of the former Tran Van Thoi district. *Photo: An Minh*

Nguyen Canh Hanh, Vice Chairman of the People's Committee of Da Bac commune, stated that the rainy season coincides with rice sowing, prompting residents to discharge inland water into canals. All irrigation sluices open simultaneously to reduce pressure. The strong flow of freshwater into the sea creates a difference, pushing the saltwater layer further away and forming two distinct colored sections.

Da Bac commune leaders confirmed this is a natural phenomenon, not environmental pollution, and it typically subsides by the end of the month. The area features nearly 10 irrigation sluices that connect inland waterways to the sea.

Local residents explained that water from the U Minh Ha freshwater conversion zone contains high levels of alum and alluvium, giving it a characteristic reddish-brown color. When this water meets saltwater, the two currents do not mix immediately, creating a prolonged demarcation line.

Chuc Ly