The first one of those I ever saw was in Northern Ireland. Dad didn't know what it was, but it was in my Ladybird car book - instatnt recognition on my part. It was dripping water along the road, had just come out of Lough Neagh...
Only others I've seen have been in museums (the Lakeland has at least one)...
Visions of beating a traffic jam by driving into a river and bypassing it!
I have visions of incompetent SatNav followers being able to continue their journey after driving into a canal

Wasn't there a recent TV prog (last 2 or 3 years) about the restoration of one of these?
Cheers,