A rare occurrence of “red tide” phenomenon witnessed by locals in the island commune of Phu Quoc. Photo courtesy of local residents.

According to the leader of the island commune of Tho Chau, this phenomenon is a rare sight, as a vast area of the beach’s water turned from green to red, creating an unusual spectacle. Before reporting to the local authorities, islanders captured these images, a first for this island.

“Red tide” is caused by an algal bloom, where algae reproduce in large quantities, changing the color of the seawater. Depending on the type of algae, “red tide” can produce toxins to varying degrees.

The “red tide” phenomenon can be harmful to marine life in the area where the algal bloom occurs. Photo courtesy of local residents.

The toxins released during a “red tide” can deplete oxygen levels in the water, threatening the lives of aquatic and marine organisms in the vicinity of the bloom.