Abstract: This invention relates to a small scale semi-submersible boat for naval combat comprising a hull of which a first, water-tight part is insubmersible and a second part is submersible.In the submersible part of the hull is accommodated at least one balloon or caisson serving as float which has a wall capable of being perforated and is inflated by means of a gas to enable the boat to float, the said boat also having a device for perforating the wall of the aforesaid balloon or caisson of a similar boat of an opponent, so as to damage the buoyancy of the opponent's boat.