Episode 1: Karen Zemlin - Lake Superior

Recorded September 27, 2025.

In this episode we discuss how Karen Zemlin envisioned, planned and completed a new 22.9 km (14.2 mile) route on Lake Superior, from Isle Royale, Michigan to Pigeon Point, Minnesota in 6 hours and 12 minutes on August 13, 2025.

We talk about how this route differs from the already established east and west routes and what makes it an excellent addition to the options for ultraswims in the world’s largest lake.

Karen shared with us how the unique geography of the lake contributed to an upwelling as she swam toward shore, resulting in a twenty degree temperature drop down to 46°F (8°C). We learned how she coped with the cold and how her crew supported her in completing the swim safely.
Some links to resources that were mentioned during the episode:

- Official documentation from Karen Zemlin’s Lake Superior swim: https://marathonswimmers.org/swims/2025/zemlin-isle-royale
- Karen Zemlin's LongSwims Database profile: https://longswims.com/p/karen-zemlin
- Website for the Marathon Swimmers Federation (MSF): https://marathonswimmers.org
- Other MSF documented swims: https://marathonswimmers.org/swims/
- Jessica’s post on hypothermic swimmers losing consciousness on marathon swims: https://oregonlakebagging.wordpress.com/2021/01/09/swimming-to-confusion-stories-from-cold-water-swimmers/