Clarence Giles was a livestock auctioneer and American open water swimmer who is a member of the 24-Hour Club.
- Giles swam 88.5 km (55 miles) down the Yellowstone River in Montana on 4 September 1938 in 12 hours on a bet at the age of 44.
- Giles completed the greatest distance covered in a continuous open water swim where he traversed 288 miles (463.4 km) from Billings, Montana to Glendive, Montana in the Yellowstone River in 77 hours 30 minutes, finishing on 4 July 1939 according to the Guinness Book of Records at the age of 45.
- He broke the records of Pedro A Candiotti who swam 281 miles down the Parana River from Santa Fe to Zarate in Argentina in 84 hours in 1933 and American Charles Zibelman who swam 145 miles down the Hudson River from Albany to New York City for 148 consecutive hours in 1935.
- Down The Yellowstone River
- Clarence Giles Navigating Rapids Of The Yellowstone River
- In River Nearly 90 Hours, Sets 292-Mile Mark
- 24-hour Club…Swimming All Day And Night
- International Marathon Swimming Hall of Fame
- Marathon Swimming
- World Open Water Swimming Association
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