Hydrogen sulfide (H2S) is a molecule dissolved in many thermal spring waters at variable concentration. The H2S effects of thermal waters treatments have long been studied, for dermatological and clinical treatments, but its role in recreational waters was never investigated. The use of sulfur spring waters in pools raises concerns related to disinfection by oxidants. The aim of this work is to evaluate the survival rate of microbial species in waters with different titers of H2S. Four selected thermal waters collected from Italian springs, belonging to different chemical categories, have been tested in comparison to Tyrrhenian sea water and natural mineral bottled water. Results show inhibition properties on bacterial proliferation that seem related to H2S concentrations. To further asses this phenomenon H2S was added to thermal and natural mineral waters. The results strongly support a bactericidal role of H2S in thermal spring waters used for recreational purposes. These observations open up new perspectives for a disinfectant role of H2S in pool treatment and management.