Okay so now the best hypothesis is that it is not Pirates but actually brain cells and neurons??
Cool I always thought it was intelligent to put a pond in. Now I have the proof for my wife who thought it was a stupid idea.
Now I can tell her I am fostering a big large brain as opposed to a hole in the ground to put money into.
On a more serious note, the holes in mine have not frozen over as of yet, but I also see the spider type of marks from one to the other. I would truly love to see some scientific study or description of what is happening in the pond as we see such things.