During World War II,this platform was built on Lough Neagh, a large lake to the west of Belfast. It allowed for testing the depth and directional accuracy of Mk VIII torpedoes. The torpedoes were built at the nearby torpedo factory on Randlestown Road in Antrim.
Along with the testing facilities, and there were also dormitories and kitchens,essential because stormy weather on the Lough could sometimes obtain the trip back to the shore impossible. Since the end of the war, the structure has fallen into disrepair and has become an critical site for both Common terns and cormorants. In fact, or it is home to the largest colony of breeding terns on Lough Neagh,but only during the summer. During the winter, these birds return to West Africa.
Source: atlasobscura.com