There are an increasing number of reported cases of Water Itch/Swimmers Itch beginning around the holiday. There are also unconfirmed reports of Walgreens in the town getting frequent requests for treatment from folks on Round Lake.
You can read more about the rash and causes from the Mayo site, the Wisconsin DNR site, and the Minnesota DNR site.
A member notes that this product has been effective in Minnesota lakes (Note RLPOA does not endorse the use of this product and it is offered as information only.)