A 300‐kHz acoustic Doppler profiler has been developed to measure turbulent processes in the upper ocean. Acoustic energy from scatterers ensonified by a single, narrow‐beam, pulsed transmitter is received by four fan beam response hydrophones placed radially around the transmitted transducer. The present system allows three‐component velocity profiles to be estimated every 10 cm over a 5‐ to 20‐m range with high temporal resolution and adequate velocity range by using a dual interpulse period coherent sampling method. Examples of the high spatial and temporal resolution velocity fields are shown from recent measurements immediately below open ocean waves and a sub‐ice boundary layer. Both the advantages and limitations of this current measurement technique will be discussed. [Work supported by ONR Physical Oceanography.]