The Black Sea is one of the main recreational facilities in Russia subject to a high annual anthropogenic stress. Anthropogenic activity led to high coastal sea waters pollution, eutrophy, and endangered the sea’s self-purification capabilities. The total quarantine introduced on the Black Sea coast of the Krasnodar territory associated with the new coronavirus infection COVID-19 pandemic led to a decrease in anthropogenic pressure on coastal ecosystems and provided a unique opportunity to trace the dynamics of the most important hydrochemical indicators of coastal waters in the Tuapse district. The study aimed to characterize the impact of quarantine measures against the coronavirus on the state of coastal waters in the eastern part of the Russian Black Sea. For this, we identified and characterized the hydrochemical indicators and determined the effect of quarantine measures on their dynamics. The study used the standardized methods. The results obtained showed that a decrease in the recreational stress led to a proportional decrease in the pollutants supply to coastal sea waters; with the recreational stress resumption the concentrations of mobile pollutants tended to increase; a proportional relationship was established between biochemical oxygen demand (BOD5 ) and the ammonium nitrogen (NH4+) concentration; the nitrates’ (NO3–) concentration, in the seawater did not depend on the recreational stress degree. In particular, a proportional increase in NH4+ concentration and BOD5 in seawater was detected: in the third quarter of 2019 the concentration of NH4+ and BOD5 amounted to 3.0 mg/dm3 and 8.5 mg/dm3 , and 3.8 mg/dm3 and 7.5 mg/dm3 in the fourth quarter, respectively; in the 2020 samples, a decrease in the NH4+ concentration to 0.8 mg/dm3 in the third and to 1.2 mg/dm3 in the fourth quarter led to a proportional decrease in BOD5 4.5 mg/dm3 and 3.9 mg/dm3 , respectively. Thus, it was shown that the quarantine measures were shown to have a positive effect on the processes of self-purification of coastal sea waters in recreational zones.