A new thermistor flowmeter can measure current speeds from 0.2 to 50 cm s‒1 with a spatial resolution of 0.1 cm and a response time of 200 ms. The output of the meter approximates a logarithmic function of the ambient water velocity. The flowmeter itself has a low power consumption and the output can be stored on magnetic tape using a battery‐powered cassette recorder, making possible a continuously recording portable or self‐contained underwater unit.