At first glance, the concrete piles lying off the coast of southeast Essex, near the town of Shoeburyness, looks like the exposed columns of an old pier, but in reality is a defensive structure erected across the mouth of river Thames to prevent ships from crossing into. At one time, this so called “boom” extended all the way to the other side of the water channel to Sheerness in the Isle of Sheppey.

The Shoeburyness boom across Thames estuary. Photo: Andy119/Shutterstock.com