Petkov, 64, swam 3,380 metres in Macedonia’s Lake Ohrid, beating the record of Indian fisherman Gopal Kharvi, who in 2013 swam 3,071 metres in the Indian Ocean - though not in a sack.
The Bulgarian swimmer already had one entry in the Guinness Book of Records in 2013 with 2,030 metres, but he only held it for three months until he was overtaken by Kharvi.
Before his latest attempt, Petkov said he had planned to swim 3.5 kilometres, and Guinness observers were present for his swim, organised by the Red Cross and the waters sports clubs of Ohrid and Petric.
Petkov took around three hours to worm his way along through the water, face-up and feet first, before he emerged on the shore in the ancient town of Ohrid, a popular holiday resort.
(Reporting by Ognen Teofilovski; Writing by Aleksandar Vasovic; Editing by Hugh Lawson)
