Adrian,
You wrote: 'What do folks do when it's super-cold and they're wearing waterproof insulated shoes/boots? Just avoid water?'
I tested this situation on a day hike a few months ago, in 25F temps. I took off my trail sneakers and socks and put them in my pack, along with my pants (the water seem high enough to warrant that), donned my Mary Jane Crocs and still wearing a pair of shorts, went in.
At first I had to cross a small side slough before crossing the main part of the creek (the creek being about 75 yards across). My feet got cold immediately, but that was to be expected. To my surprise I felt my legs hitting and then breaking branches underwater. I was momentarily stunned and then saw a thin sheet of ice break at the surface as my thighs moved up and down while taking steps.
It took a second or so before I realized that the 'branches' were really the ice that I was breaking as I walked. It was covered by some water and not readily visible.
I then crossed to a gravel bar, and proceeded across the main creek. Exiting, I had a towel at the ready and was prepared for a lightning footwear change. Which was, to my surprise, unnecessary. In 4 to 5 seconds out of the water my feet were warm. I never bothered with the towel.
I sat on a log, took out some hot chocolate and a snack and proceeded to eat for about 5 minutes, still in my Crocs. When, done I changed back into pants, socks and trail sneakers, put the Crocs back in the pack and continued on.
I told people about this when I got back, but have a reputation for going a bit beyond the limits, and so was quietly dismissed.
A month later on a backpacking trip, only one of a half dozen hikers with me chose to take the route requiring the stream crossing. His comment: 'I've been carrying these Crocs the entire trip and I'm going to try them out!'.
And so he did. We crossed a creek with the same results as last time – a leisurely changing of socks and shoes afterwards. But when he told the story at the restaurant after the hike, no one dismissed it. On the other hand, no one seemed eager to try it either.
Marty Cooperman

