I have some reeds still on land, at the edge of the pond (you can see where I sketched in their shadows already) and then I get to work on the pond itself.
I was thinking about how snow sits on top of ice, and then melts into it a little, so that the top is quite white, but some places are black with ice. Places where people tossed rocks to see if it was thick enough to skate on, or sticks fell on it, or small creatures left small footprints, all those show up as divots with black at the bottom. What I have to begin with is four layers of silk organza dyed black, gray and white. The rock sits in the pond a little, so the ice has melted around it and refrozen.
I'm still thinking about how to do this part. I may try something that is removable, if I feel very dubious.