The boat owned by Hoang Van San from Quang Nham Commune in Quang Xuong District, sank at around 1 pm on Sunday after encountering a whirlwind.
As a result, all eight people on board fell into the sea. Four were rescued but the remaining four have still been unaccounted for.
Local authorities of Thanh Hoa have called for co-operation from Quang Ninh Province and Danang City to search for the missing.
