The laser beam is actually invisible unless it is reflected off something. The beam seen in the air is reflecting off dust in the air, in a vacuum it would be invisible. A screen, wall, smoke, net screen (scrim), even clouds if the laser is powerful enough, can be used and the systems offered can be used in this way. However water offers a unique sparkle and brightness, also the images appear out of nowhere, suspended in the air. The water is invisible unless the laser hits it. With vertical and centre fed water screens a large or very screen can be made without any infrastructure, no surface, no construction, no gantry, it is in place at the touch of a button and invisible until the laser hits it.