H2O is just the scientific notation for water. In scientific terms, the clear liquid would be named Hydrogen oxide. Here, in this picture, the liquid shows its dual nature, where it is both reflective and transparent at the same time. Such is the nature of water.
H2O vs. Water
P.S. Some writers, such as Bill Bryson, have referred to water as Dihydrogen oxide. This wording seems to be functionally correct without any scientific precedent. If water has a basic or acidic quality, then it may be called Hydrolic hydroxide or Hydroxic acid. Since the water in this picture is probably acidic it may be referred to as Hydroxic acid.