Mark Johnston may not have had the best of luck during his attempt to swim the length of Flathead Lake three weeks ago, but last Friday, he guided two of his friends though 15 hours of a grueling swim on the lake.

Sarah Thomas and Craig Lenning both finished the 28-mile swim. Neither wore wetsuits or had assistance of any kind. They were the first ever to do so. Thomas finished the swim in 13 hours and 45 minutes. She was about two hours ahead of Lennings, who finished in 15 hours and 30 minutes.

The swimmers started their swim at 3:45 a.m. on the morning of July 3, and swam through the day, with temperatures rising up to around 95 degrees. Cold water wasn’t an issue, as Flathead has water temperatures above average this year. Lenning said the water was between 72 and 76 degrees. “It was tough swimming. The warmer it is, the more you sweat and your muscles cramp up,” he said.

Lenning, who has swam the English Channel before, said it was about as good of a day as they could have hoped for. “The wind was blowing us north to south. We never really had a headwind,” he said.

It was Lenning’s first time to Montana, and he said he would like to come back. “It is a beautiful lake,” he said. Next time he comes back, he said he might skip the swim and instead do some kayaking or fly-fishing.

Thomas has been a competitive swimmer since she was young. In 2010, she did her first ultra marathon, which was over 20 miles long.

She has also swam the English Channel, and said Flathead was actually harder. “We really struggled with the heat,” she said.

Thomas and Lenning are training to swim Loch Ness, which is about 23 miles. Thomas said they were looking for a cold-water lake to train in, and Flathead was a good choice. “It was a very pretty lake,” Thomas said of her first trip to the lake. “Although it wasn’t very cold.”