Certainly the Car Plunge is a neat idea, and our own Ice Out Contest is certainly an item of interest. Whenever I think ice out, I am reminded of my time spent stationed at an Air Force base outside Fairbanks. A tripod is placed out on the ice in the Tanana river in Nenana AK, and when the ice moves sufficiently to stop a clock that is connected on shore to the tripod by rope or cable, the person who guesses the correct time the clock stops, or closest time either side of that time.
I was in Alaska from 1967 to 1972, so this ice out contest has a lot of history. In fact, it dates back to 1917. In fact, this weekend is Tripod weekend, with activities all weekend. Later today, the Tripod will be placed on the Tanana River. They even have a webcam overlooking the site.
Here's a link to the Nenana Ice Classic website.
https://www.nenanaakiceclassic.com
Dave