This naval mine is similar to those that were used by the Allied forces during World War II as a way of defending the coastal shores.

These types of mines were self-contained explosive devices that floated to the top of the sea, while anchors called sinkers kept them from floating away. They were triggered by approaching ships or from direct contact with vessels. The mines were also utilized to create safe zones. This was when a series of mines were used to protect shipping routes or a specific area of the coast. 

The mine present along the Marine Highway in Carrickfergus is an MK14 Sea Mine. It features a 1920s design constructed from two large iron sheet metal hemispheres, with a metal belt between them. The mine also had many horn-like projections protruding from its bulk called Hertz Horns. These acted as contact triggers when floating in the water.

Eventually, the mine was converted into a collection box by The Shipwrecked Mariners Society, who placed it in the gardens near Carrickfergus Castle to help support local charities. Carrickfergus has a rich military heritage which it proudly showcases to the general public with items such as the 25Pdr Field Gun, Churchill MK VII Tank, Carrickfergus Castle, Sullatober Mill, along with many others across the town.