If the Purifying Tonic is water-based, how can it be certified organic? 

Water does not count for or against the calculations in the USDA NOP rules. There are many ingredients in Purifying Tonic, including essential oil/ aroma and the Intellimune® seed flour powders. In order to use the USDA seal, Intelligent Nutrients® must show that 95% of the ingredients (not including water) are certified organic.