You sure about one hour? Here are some world records. These are open water swims but still, look a the times for close to 5 miles.
Open Water Source
World Open Water Swimming Records (AMERICAS)
The list below is a short list of open water swimming records (under 10 kilometers) donewithout wetsuits and according to traditional English Channel rules in the Americas. With over 70% of the Earth covered in water, the number of records and locations to swim arenumerous and potentially endless.If you know of any additional records or new records that have been set, please email thename of the world record holder, their country, date (month, day and year), location, distanceand official time toOpen Water Source.
Waikiki Roughwater Swim (2.4 miles, Honolulu, Hawaii, U.S.A.)
Fastest Male: Daniel McClellen (Australia), 1995, 42:13Fastest Female: Lisa Hazen (USA), 1995, 45:33
RCP Tiburon (1.2 miles, San Francisco, California, U.S.A.)
Fastest Male: Vladimir Dyatchin (RUS) 2007, 18:20.00Fastest Female: Chloe Sutton (USA) 2007, 19:04.70
Golden Gate Bridge Crossing (San Francisco, California, U.S.A.)
Fastest Crossing: Bob Roper (USA), 1969, 17:21
Willoughby Swim (4.75 miles, Lake Willoughy, Vermont, U.S.A.)
Fastest Crossing: Charlotte Bryne (USA), 21 August 2010, 2:09.50
Kingdom Swim (3 miles, Lake Memphremagog, Vermont, U.S.A.)
Fastest Swim: Tim Walsh (USA), 24 July 2010, 1:12:48
Beagle Channel (Argentina to Chile)
First One-Way Crossing: Lynne Cox (USA), 1990First Two-Way Crossing: Rachel Golub (USA), Patricia Sener (USA), Cristian Vergara(Chile/USA), 2010