Chaun Bay in the outskirt of the East Siberian shelf has been known since the middle of the last century as a sea bay with unique marine biocenoses, not typical of the local severe climate with its sparse biogenic sources. Here we present the data covering the following parameters of the bay seawater: salinity, dissolved oxygen and carbonate system parameters; radium isotope activity and its ratios (²²⁴Ra/²²⁸Ra, ²²⁴Ra/²²³Ra), as well as radium age; dissolved metals concentrations; nutrient concentrations; δ¹⁸O and δD.