According to Ihor Krol, a spokesman for the emergency situations ministry, the Mi-8 helicopter was carrying a crew of three and 10 passengers from the southern city of Odessa when it crashed into shallow waters near Poludenniy Island just before noon.
Sergiy Shmorgal, a spokesman for the emergency ministry in the southern port of Odessa, where the helicopter took off, said that the helicopter crashed at around 11.30am local time (0930 GMT).
Rescuers found 12 bodies near the site of the crash.
The only survivor is in a coma.
Crashes of the Mi-8 - a helicopter used widely in civilian aviation and the military - occur frequently in the Ukraine and Russia and are often blamed on poor maintenance.