The Open Water Swimming Marathon Kalamata – Koroni is a marathon swimming competition in Greece. It has been held for 29 years in the Messiniakos Gulf and is sponsored by the Nautical Club of Kalamata by race organizer Dimitris Kakalikas. It is one of the World’s Top 100 Open Water Swims. The 30 km point-to-point race between Kalamata and Koroni in northern Greece is also known as the Swimming Marathon of the Messinian Gulf or Κολυμβητικός Μαραθώνιος. The amateur race is traditionally held in early September. Two-way and three-way solo crossings have also been attempted.