Aqueous organic chemistry (AOC) has received considerable attention in the past few decades because it represents a cheap and accessible green alternative to traditional organic solvent chemistry. Though AOC was originally developed for reagents that are soluble in water, the field has expanded to include reactions where reactants are not necessarily miscible with water. In this context, the “on water” effect occurs when an organic reaction is accelerated in the presence of a water-organic interface compared to the same reaction in an organic solvent or solventless conditions. Although some mechanisms have been proposed to explain this effect, there is still no agreement on the molecular origin of this phenomenon. Understanding the chemistry involved in heterogeneous aqueous-organic media has important implications in biochemistry, prebiotic and atmospheric chemistry. This talk will explore some of the experimental and computational efforts toward understanding the “on water” effect.