A barrier structure assembly (10) for use underwater, the assembly comprising a barrier screen (15) and a set of upper floats (17), which, in use, are connected to an upper edge of the barrier screen, a set of lower anchoring elements (20), which, in use, are connected to a lower edge of the barrier screen, a set of intermediate floats (19), which, in use, are connected to a first fold-line of the barrier screen between the set of upper floats and the set of lower anchoring elements. A first lower portion (22) of the barrier screen (15) extends between the set of lower anchoring elements (20) and the set of intermediate floats (19). The assembly also includes a set of intermediate weights (18), which, in use, are connected to a second fold-line of the barrier screen between the set of intermediate floats (19) and the set of upper floats (17). A second middle portion (23) of the barrier screen is provided between the set of intermediate weights (18)and the set of intermediate floats (19), and a third upper por
