"The reason for this tragedy were storms and an absence of life jackets. Twelve people drowned and one is missing," said Volodymyr Jmak, a deputy of the governor of Odessa region. He added that the vessel had been transporting 36 people, including three crew, when it sank mid-afternoon.
Jmak said the remaining 23 passengers were safe of whom 18 were in hospital.
Regional governor Mikhail Saakashvili, the reformist former president of Georgia and now a Ukrainian citizen, said in a post on Facebook that he would cut short a visit to the western city of Lviv to head for the scene at Zatoka, a village some 50 kilometres (31 miles) from Odessa.