I spent 3 and a half minutes immersed in 11.8 degree Celsius water. My friend was impressed that I did so well for my first time, but it seemed too easy to me. When I got out I felt like I could do at least 2-3 minutes more, but he said 3 minutes was enough for now. Hopefully I'll get down to 0 Celsius before too long.
If you want to read more, subscribe to my personal newsletter.