Martin Riese is the only certified water sommelier based in the United States. He has curated a list featuring 20 of the world's finest waters, which he sells for up to $20 a bottle at his Los Angeles restaurant. Riese began his renowned career in his native Germany. Today, he is a Water Tasting Educator, acclaimed author, Water Sommelier at Patina Restaurant Group in Los Angeles, and the world’s foremost expert on water. So what is a water sommelier? What is it like to be a professional in water-tasting? And can you really tell the different tastes of water? Audrey Raj finds out.