Conversion of light to thermal and mechanical energy in the vicinity of the water-air interface was studied experimentally. The focus of an IR pulsed laser was moved in steps in vertical direction from the position inside the water upwards to the position slightly above the surface, in the air. The generated optodynamic waves were detected by probe beam deflection. Two probe beams were used simultaneously, both laying parallel to the surface, one inside the water and the other one in the air. The analysis and comparison of the waveforms captured in the two media provide information about the position and size of the optodynamic source relative to the interface, indicating the relative efficiency of thermal energy conversion that takes place in the vicinity of the interface both in the air and inside the water. Three positions of the optodynamic source can be determined from the waveforms: in the air, at the interface and inside the water. (c) 2007 Elsevier B.V. All rights reserved.