Moving water and the light playing of the waves. A few years ago, I started experimenting with different shutter speeds, trying to capture the movement well, without loosing details. The shutter speed needs to match the speed of the water or the image is too soft. Doing so in the winter is a particular challenge, since long exposures can blow out all the whites. That said, I like the soft winter light.
The photo above was made at Duffins Creek, in north Pickering, Ontario. Most of the river was frozen but there were a few open patches. This is a fairly tightly cropped view of one of those places.
Tamron 70-200 mm f/2.8 @ 130 mm
1/8 sec, f/32.0, ISO 250