Nguyen Tuan Thanh from Hoa Tan Commune, Ca Mau City, spotted the animal on the Ganh Hao River at around 9.45 am on Friday.
The animal weakly swam around for about half an hour before disappearing, Thanh said.
The dolphin is spotted on the Ganh Hao River on June 27. (Photo by CTV)
Following Thanh's report, local authorities dispatched officials to the area to assess the situation.
According to residents, dolphins are typically found at sea, and this is the first time they have witnessed one swimming into a river approximately 50 kilometres from the Ganh Hao Estuary. The animal is believed to have strayed due to rough sea conditions.
About 10 dolphins stranded off Cai Cung coast in the southern province of Bac Lieu were rescued and returned to the sea by locals in November last year.
