Martyn Webster - Flathead Lake

Somers to Polson

44.5 km (27.7 miles)

14 hours, 30 minutes on 19 July 2023

Observed and documented by Rachel Wanderscheid and Cat French



  • Name: Martyn Webster
  • Gender: male
  • Age on swim date: 56
  • Nationality: United Kingdom
  • Resides: Rapperswil, Switzerland

Support Personnel

  • Mark Johnston - boat pilot / organizer
  • Rachel Wanderscheid - observer 1 / paddleboard support
  • Cat French - observer 2 / feed support
  • Jess Bouchee - paddleboard support


  • Rachel Wanderscheid - Open Water Swimmer. Member of Flathead Lake Open Water Swimmers.
  • Cat French - Support crew on numerous Zurich Marathon Swims, English Channel relay, Loch Awe Swim, Lake Lucerne, Lago D’Orta. Spouse of swimmer.

Escort Vessel

Name Type Port
MT6185AY pontoon Polson

Swim Parameters

  • Category: Solo, nonstop, unassisted.
  • Rules: MSF Rules of Marathon Swimming, without exception or modification.
  • Equipment used: Textile swimsuit (Funky Trunks brief), silicone cap, goggles (Swans SRX prescription), earplugs, Timex Marathon watch.

Route Definition


LongSwimsDB: Flathead Lake.

Swim Data

  • Start: 19 July 2023, 06:41:00 (Mountain Daylight, America/Denver, UTC-6).
  • Finish: 19 July 2023, 21:11:15
  • Elapsed: 14 hours, 30 minutes, 15 seconds.

Summary of Conditions

Feature Min Max
Water Temp (F) 16 18
Air Temp (F) 9 29
Wind (kph) 0 13

GPS Track

Trackpoint frequency: 20 minutes. Download raw data (CSV).

Click to expand map.

Speed Plot

Nutrition: Sponsor energy drink every 30 min. Occasional banana and peanut butter sandwiches.

Observer Log

Download PDF

Swimmer Statement

by Martyn Webster

This swim had been a long time in the planning. In first met Mark Johnston in 2017 when he was a guide on the SwimTrek Channel and Distance training camp. Mark lives on Flathead Lake in Polson, Montana and to be honest I had never heard of the lake. One year later we met again and started talking about the possibility of swimming the lake. However, at that point I couldn’t see when I could fit it in with swims committed years in advance and trying to balance my work as a company director and my family commitments, I could see the possibility until 2020

2019 we met again talked more about Flathead when Mark come to Switzerland, to swim the Rapperswil to Zurich Swim Marathon, and then 2 weeks later when Mark crewed for me on my North Channel Swim. The date was tentatively planned for 2020. But then COVID happened and I had commitments already for 2021 and 2022.

After SCAR is 2022 followed by a short trip to Montana in 2022, we agreed on the summer of 2023 and a date in July.

Once agreed the planning was straight forward. Flights were booked and that was it. Mark knows me well and my swim style and capabilities. So, I left it all to Mark to arrange crew and the local logistics.

Mark has his own pontoon boat, is an experience marathon swimmer and master’s coach and as is part of the Flathead Lake Open Water Swimmers Group – from which we had a good group of swimmers ready to crew together with my wife Cat.

On board we had the luxury of 4 crew and the possibility to rotate people around between pontoon board and paddleboard

We allocated a week to be in Montana and had the luxury of being able to select from a couple of good weather days.

Prior to the swim we had not decided on direction – I was happy to swim either direction. But settled on the 19th as the best weather day all round with a bit of a push from the North

The day we selected was as forecast. Cold start - water 16/air 13 deg C, but warming up to 18/30 respectively, and wind wise wit was blowing a little east to west to start but then changed from north to south giving me a nice push along for 1/3 of the swim.

Everything went according to plan. I have my usual 2 hr. period where I think ‘WTF am I doing this for?’ Especially when the wind was blowing waves into my face and I couldn’t get any real rhythm. Then the wind changed, and I felt like I was surfing with the wind pushing me down the lake. The last 2/3 of the swim the wind dropped to almost nothing and I was able to get my head down and focus on my stroke, rhythm, enjoy the swim and just get in that flow state. , In the days prior to the swim we had done a bit of a reccie and looked at the map in detail and I had basically divided the swim into 4 sections in my head.

10km - to Angel Point 10km - to Cedar Island 15km - to get through the Narrows 10km- the home run across Polson bay to the finish

So, these were my ‘mental’ milestones I was focused on.

Feeding went well. My feeds are simple. I only use a starch-based energy drink from Swiss company Sponsor and have either banana or peanut butter sandwiches. Basically, I am feeding every 30 mins – with solids every 2 hours. I change it a little, but only if I feel like it during the swim. All went to plan with feeds and peeing. So I felt very comfortable in the water.

Flathead is a beautiful Lake and I was able really enjoy the scenery along the shorelines and especially some of the big houses that line the Narrows. Oh, how the other half live?’


Click to enlarge.