Ice freezes in flat sheets down on the old fjord lake. A few days later, it is broken up by the wind, in angular chunks, as the repeated rising and falling, linear energy of the waves is translated into long, linear pressure fractures.
Still waves, right? Then water rises through the angular cracks and contours them most beautifully.
And so the waves become rivers and islands. This is an estuary landscape! When it dissolves, as estuaries do, there will be open water again.