Experimental values have been obtained for the thermal noise spectrum of water in the 1.0–2.5 Mc frequency range. The procedure was based on measurement of the radiation resistance of thin‐disk transducers loaded by water. A comparison is made with the theoretical thermal‐noise spectrum of an ideal medium calculated by assigning equipartition energy to the acoustic modes. Agreement to better than 3.6% was found between the experimental values and the theoretical spectrum.