Plot device in a Neil Gamen book IIRC Edit: the book was American Gods and it's Gaiman. Interesting read...

Reminds me of this fun local tradition in Nederland, CO:
https://en.wikipedia.org/wiki/Frozen_Dead_Guy_Days
https://frozendeadguydays.com/

I've got friends in the north near Kirkland Lake, Ontario and they do a similar annual fundraiser with a Volkswagon Beetle - they've been doing it for years with the same car. I think it's for fundraising for their local fire department.

Kenogami & District Volunteer Fire Brigade - Herbie Car Fundraiser

The car is cleaned up and cleared for environmental pollutants and then fished out every spring and repeated again the next winter. I always thought it was funny seeing that old yellow car on the ice.

That's neat! We just have a sign on the river, and people guess when the ice will start moving. More precisely, when the sign will pass under the bridge. A dummy would definitely be more fun, but some teenagers would probably steal or break it... or someone would mistake it for someone drowning in the spring as it travels towards the sea. Maybe it's better to just stick to the sign.