Flathead Lake

From Openwaterpedia
Emily von Jentzen doing a charity swim in Flathead Lake, Montana

Flathead Lake is the largest natural freshwater lake in the western part of the contiguous United States. With a surface area of about 191.5 sq mi (496 km2), it is slightly larger than Lake Tahoe. The lake is a remnant of the ancient inland sea, Lake Missoula of the era of the last interglacial.

Flathead Lake is 27.3 miles (43.9 km) long and up to 15.5 miles (24.9 km) wide with a maximum depth of 370.7 ft (113.0 meters), making it deeper than the average depths of the Yellow Sea or the Persian Gulf and about half the area of San Francisco Bay (main bay). The lake was raised 10 feet (3.0 meters) by Kerr Dam and is one of the cleanest in the populated world for its size and type.


Located in the northwest corner of the state of Montana, 7 miles (11 km) south of Kalispell, it is approximately 30 miles (50 km) long and 16 miles (25 km) wide, covering 191.5 square miles (495.9 km²). On the west side, the lake is flanked by U.S. Route 93, and on the east, by Route 35. The lake is bordered on its eastern shore by the Mission Mountains and on the west by the Salish Mountains.

Open Water Swimming

Length Crossings (25 miles)

Swimmer Name Date Time Details
1 Paul Stelter (Assisted) 20 Aug 1986 14:15 [1]
2 Ron Stevens (Assisted) 16 August 2005 12:25 [2]
3 Emily von Jentzen (Assisted) 17 July 2010 18:26 [3]

Vampire Swims

Flathead Lake is one of the global locations of the Vampire Swims, a series of open water swims held on 31 October.

Vampire Swims are also a great way to kick off the cold water, winter swimming season in those locations where swimming continues year round. Entry fee for these swims will include proof that the swimmer has donated blood within 6 weeks prior to the swim. Some venues are arranging a blood mobile to collect donations immediately after the swim. Those who cannot make a donation of blood for medical reasons can make a cash donation to the Red Cross or some other similar organization. A US$10 registration fee will also be expected of each swimmer to cover the cost of a custom, bloody-toothed swim cap and other incidental expenses with any remainder also to be donated to the Red Cross or other equivalent organizations that collect and distribute blood.


• Newport, Vermont (Lake Memphremagog) (Phil White)
• Boston, Massachusetts (Greg O’Connor)
• New York, New York (Jaimie Monahan)
• Westport, Connecticut (Liz Fey)
• Ottawa, Ontario (Nadine Bennett)
• Kingston, Ontario (Deborah Durbin)
Loch Ness, Scotland (Helen Beveridge)
Loch Lomond, Scotland (Chris Sifleet)
• Flathead Lake, Polson, Montana (Mark Johnston)

Ultimate Swim-a-Thon

The Ultimate Swim-a-Thon is a 50-state, 50-swim extreme charity swim by American open water swimmers and brothers Joseph Zemaitis and John Zemaitis from Arizona (also known as the Swim Brothers). The Ultimate Swim-a-Thon requires the completion of a marathon swim of at least 10 km in distance in all 50 states. The charity swim benefits USA Swimming Foundation.

  • Day 1 (20 July 2022), Swim 1: 10.2 km from Makaha Beach to Keawaula Beach on Oahu, Hawaii
  • Day 2 (21 July 21st), Swim 2: 10.33 km in Big Lake, City of Anchorage, State of Alaska
  • Day 3 (22 July 22nd), Swim 3: 10.41 km in Lake Tahoe, City of Reno, State of Nevada
  • Day 3 (22 July 22nd), Swim 4: 10.06 km in Lake Tahoe, State of California
  • Day 4 (23 July 23rd), Swim 5: 17.16 km in the Willamette River, Portland, State of Oregon
  • Day 4 (23 July 23rd), Swim 6: 10.32 km in Yale Lake, City of Yale, State of Washington
  • Day 5 (24 July 24th), Swim 7: 10.00 km in Coeur d’Alene, City of Coeur d’Alene, State of Idaho
  • Day 5 (24 July 24th), Swim 8: 10.43 km in Flathead Lake, City of Elmo, State of Montana
  • Day 6 (July 25th), Swim 9: 10.38 km in Lake de Smet, City of Sheridan, State of Wyoming
  • Day 6 (July 25th), Swim 10: 10.30 km in Belle Fourche Dam, State of South Dakota
  • Day 7 (July 26th), Swim 11: 10.35 km in Lake Ashtabula, Valley City, State of North Dakota
  • Postponed due to Lightning: Day 7 (July 26th), Swim 12: 10.08 km in Lake Minnewaska, Glenwood, State of Minnesota
  • Postponed: Day 7 (July 26th), Swim 13: 10.05 km in Spirit Lake, City of Spirit Lake, Iowa
  • Day 8 (July 27th), Re-do Swim 12: 10.08 km in Lake Minnewaska, Glenwood, Minnesota
  • Day 8 (July 27th), Re-do Swim 13: 10.05 km in Spirit Lake, City of Spirit Lake, Iowa
  • Day 9 (July 28th), Swim 14: 10.22 km in Lake Michigan, City of Kenosha, State of Wisconsin
  • Day 9 (July 28th), Swim 15: 11.97 km in Lake Michigan, City of Waukegan, State of Illinois
  • Day 10 (July 29th), Swim 16: 10.08 km in Lake Michigan, Michigan City, State of Indiana
  • Day 10 (July 29th), Swim 17: 10.21 km in Lake Michigan, New Buffalo, State of Michigan
  • Day 11 (July 30th), Swim 18: 10.12 km in Lake Erie, City of Conneaut, State of Ohio
  • Day 11 (July 30th), Swim 19: 10.24 km in Lake Erie, City of Erie, State of Pennsylvania
  • Postponed: Day 11 (July 30th), Swim 20: 10.24 km in Lake Erie, City of Westfield, State of New York
  • Day 12 (July 31st), Swim 20: 10.24 km in Lake Champlain, State of New York
  • Days 12/13 (July 31st/August 1st), Swim 21: 10.20 km in Lake Champlain, State of Vermont
  • Day 13 (August 1st), Swim 22: 10.13 km in Lake Winnipesaukee, State of New Hampshire
  • Day 13 (August 1st), Swim 23: 10.08 km in Lake Sebago, City of South Casco, State of Maine
  • Day 14 (August 2nd), Swim 24: 10.16 km in Narragansett Bay, State of Rhode Island
  • Day 14 (August 2nd), Swim 25: 10.04 km in Buzzards Bay, Pocasset, State of Massachusetts
  • Day 14 (August 2nd), Swim 26: 10.08 km in Long Island Sound, Norwalk, State of Connecticut
  • Day 15 (August 3rd), Swim 27: 10.06 km in Silver Bay, City of Toms River, State of New Jersey
  • Day 15 (August 3rd), Swim 28: 10.18 km in Rehoboth Bay, Rehoboth Bay, State of Delaware
  • Day 16 (August 4th), Swim 29: 11.12 km in Eastern Bay, City of Stevensville, State of Maryland
  • Day 16 (August 4th), Swim 30: 10.46 km in Summersville Lake, State of West Virginia
  • Day 17 (August 5th), Swim 31: 10.62 km in Lake Wylie, Charlotte, State of South Carolina
  • Day 17 (August 5th), Swim 32: 10.43 km in Lake Norman, Denver, State of North Carolina
  • Day 18 (August 6th), Swim 33: 10.22 km in South Holston Lake, Bristol, State of Virginia
  • Day 18 (August 6th), Swim 34: 10.64 km in South Holston Lake, City of Bristol, Tennessee
  • Day 18 (August 6th), Swim 35: 10.44 km in Laurel River Lake, Morehead, State of Kentucky
  • Day 19 (August 7th), Swim 36: 10.62 km in Lake Burton, City of Clayton, State of Georgia
  • Day 19 (August 7th), Swim 37: 10.22 km in Lake Guntersville, Guntersville, State of Alabama
  • Day 20 (August 8th), Swim 38: 10.14 km in Choctawhatchee Bay, Destin, State of Florida
  • Day 20 (August 8th), Swim 39: 10.14 km in Bay St. Louis, Bay St. Louis, State of Mississippi
  • Day 21 (August 9th), Swim 40: 10.48 km in Toledo Bend Reservoir, Florein, Louisiana
  • Day 21 (August 9th), Swim 41: 10.16 km in Toledo Bend Reservoir, Fairmont, State of Texas
  • Day 21 (August 9th), Swim 42: 10.14 km in Broken Bow Lake, Broken Law, State of Oklahoma
  • Day 22 (August 10th), Swim 43: 10.26 km in Beaver Lake, Bentonville, State of Arkansas
  • Day 22 (August 10th), Swim 44: 10.58 km in Table Rock Lake, Branson, State of Missouri
  • Day 23 (August 11th), Swim 45: 10.09 km in Wilson Lake, City of Russell, State of Kansas
  • Day 23 (August 11th), Swim 46: 10.62 km in Harlan County Lake, Alma, State of Nebraska
  • Day 24 (August 12th), Swim 47: 10.30 km in Navajo Reservoir], Rio Arriba County, New Mexico
  • Day 24 (August 12th), Swim 48: 10.00 km in McPhee Reservoir, Fort Collins, Colorado
  • Day 25 (August 13th), Swim 49: 10.13 km in Lake Powell, Wahweap, State of Utah
  • Day 25 (August 13th), Swim 50: 10.38 km in Lake Powell, State of Arizona

External links