Killer Dolphin Hoax, News spread round the world on March 12, 2013 the escape of two highly trained and armed dolphins escaping from a secret training base on the Black Sea. However, it later emerged that the unsourced report by the Ukraine news agency RIA Novosti was based on a hoax. This didn't stop the report being published and broadcast around the world.
The idea isn't as daft as it sounds as this documentary about the former Soviet programme for training dolphins for military purposes shows:
