I'm experimenting with the interactions between convoys and escorts with the iceburgs. The iceburgs constantly drift, always on the move.
A nice game of cat and mouse between your sub and a destroyer in a tight field of moving iceburgs is going to be a real blast.
Wait until you see hedgehogs hit an iceburg.
The big iceburgs extend down into the water a good good ways. 100 ft? It becomes quite a maze in "just deep enough" waters.