For fifteen years, the prolific inventor Dean Kamen, creator of insulin pumps, heart stents, electric wheelchairs and the Segway personal transporter, has tried to solve the world’s potable water problem. (Yes, there is one, Instagram-scroller.) His newest invention, dubbed “Slingshot” to suggest the slaying of giants by technology, is a compressed vapor water purification system that requires no filters or chemicals, requires about as much energy as a hair dryer, and fits into a case the size of a dorm room refrigerator. The stylish documentary Slingshot, now streaming, chronicles the invention’s history, from gargantuan prototype to the current iteration, which includes a provocative partnership with Coca-Cola. The film will make you think and ask good questions, while providing an intimate portrait of a singular human being with a magnificent mind, someone who lives the mantra doing well by doing good.