In 1926, Ivanof signed with sports club Iraklis, as a football, water polo and swimming athlete. He eventually chose swimming above his other athletic activities. During the occupation of Greece in World War II, Ivanof was sent to the Middle East where he was trained in guerrila tactics and returned to Greece to take part in the resistance. His specialty was sabotage of ships.
Ivanof was arrested in 1941 but managed to escape. He was arrested again in 1942 and was executed at Kaisariani on January 4, 1943. He was honoured by both Poland and Greece for his heroism. His club, Iraklis, have since renamed their indoor stadium in his honour ("Ivanofio").