We analyse a new optical method to detect and utilize underwater acoustic signals from above the ocean surface. The method is based on scattering of modulated laser light by natural inhomogeneities (hydrosoles, bubbles, turbulence, etc.) whose concentration oscillates in a vertically propagating sound wave. Measurement of the Doppler shifted modulation frequency in the scattered light may be used both for monitoring of the upper ocean sound speed profile and for communication with underwater objects.