Indy and I were on the right-of-way walking along the old railroad R/W from my neighbors property to mine. The whole swamp was frozen. Well, cold enough to maintain a frozen cover to the water but warm enough to allow it to flow under the ice. On my land the path gently rises and a tiny stream of water from a spring flows along it's side. It too was entirely frozen w/ little ice waterfalls and steps. However, I came to a spot where the ice stopped and there was open slowly flowing water. Just as wooded overhead - sunlight wasn't warming the water. Must be I was near the head of the spring. The water was still "warm" from being underground and took a certain distance to cool down enough to turn to ice. Checked other nearby swampy areas - all still covered w/ ice. Interesting proof of the exact spot where the spring starts.