The Secret Harbour is located at the southern end of Wild Cat Island. It is a sheltered inlet, protected from view by high rocks and sheltered from the weather. The safe passage into the harbour is straight but narrow and hazardous. There is a string of rocks extending out into the lake which also make it more difficult to see and access. During the war between the Swallows and Amazons in Swallows and Amazons, John Walker realised that by adding lights to the secret marks, Swallow could use the harbour at night. However, it was the Amazons who eventually made use of the leading lights.