They are concrete or wooden structures that are piled deep into the ground like fondation foundation pylons on skyscrapers. The geometry part I was just referring to how they are angled in such a way it ricochets the ship away from the structure it’s protecting or towards the channel. https://sh.itjust.works/pictrs/image/73ba5bec-c718-4f0d-b353-9fa66941bd2c.jpeg