Аннотация:The article presents an investigation on the variation of 40K in the ocean. Potassium was extracted from the sea water by precipitation and the radioactivity was measured by a liquid scintillation counter. The results showed that the factors influencing the variations in the specific radioactivity of potassium in ocean waters are the influx of extraterrestrial particles to the sea and heavy influxes of potassium caused by venting of thermal waters and underwater seismic activity.