The sign made me laugh. I wasn’t tempted to swim; I saw it when it was 0C and snowing… Some midwesterners go for a polar plunge in the winter, not I.
Have you swum outdoors when the temperature is under 0C (32F)? I have not and it’s not in my plans. 😄
For my analytical readers, the waters are dangerous here because of motorboats, in warm weather. 😉