One of the three lakes that are at the back of the site with the old bridge in the far distance.
As far as i can make out it used o connect to the sea as a river but it was closed off at the far end because the beach was prone to flooding.
During the war it was still connected to the sea and i believe it was a base for the Navy who took over the beach for the duration.Indeed there is still a hint of the military camp about it albeit softened by the peace time use of many years.
The Kelts or Celts however you prefer to spell it [both are correct] made offerings to the gods by sacrificing goods in lakes,i can understand this entirely they are very peaceful and otherworldly,perhaps with a hint of danger.