As a kid, I remember going to a science museum. They had fresh water in a tank and propellers to keep the water moving. They would chill the water below 0C. At some point, the propellers would stop and ice crystals would form right before your eyes. What’s the lowest temperature that fresh water will stay in liquid form if kept in motion?
The explanation for the water all freeziing at once when moving is that when it is moving the temperature is pretty much the same throughout. Cooler but not freezing cold water in a still tank sinks leaving ice, less dense to freeze at the top first.
Not sure if that has to do with supercooled though … supercooled and suddenly freezing has to do with the lack of nucleation points in pure water. With no nucleation points the apparent answer to how cold supercooled water can get, moving or not is -48C.