The white, forward-showing light carried by a powered vessel by night or in bad visibility. In the Collision Regulations this is called a ‘Masthead Light’ (though not required to be carried at the masthead) and it must show from dead ahead to 22.5 degrees abaft the beam on each side. A vessel of less than fifty metres length may show one such light: those longer must show another similar light farther aft and higher up. A boat under sail does not show a forward white light.