I broke this piece of ice off of a larger section near shore at about noon today. While the ice was still thick and relatively strong, as soon as I pulled it out of the water and onto the rock, all the water drained out. It was very porous.
About an hour later, I lightly hit the chunk with a stick and it easily broke into these crystals. The ice became darker during the afternoon, and I expect it is approaching the point where the crystals will start to break apart.
A windy day would do it, but there don't seem to be any in the near forecast.