Although most of the diversity of true bugs (Hemiptera: Heteroptera) is terrestrial, over 550 species of water bugs (Heteroptera: Gerromorpha, Leptopodomorpha & Nepomorpha) have been recorded from Brazil alone. Southeastern Brazil, composed of the states of Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo, is the best studied region of the country, but there are still knowledge gaps in the area. Here, two new species are described from Espírito Santo: Hydrometra ruschii Cordeiro, Rodrigues & Moreira, sp. nov. and H. tuberculata Cordeiro, Rodrigues & Moreira, sp. nov. (Gerromorpha: Hydrometridae). Furthermore, new records from southeastern Brazil are provided for 78 species of water bugs, of which 19 are firstly recorded from Espírito Santo, four from Minas Gerais, eight from Rio de Janeiro, and seven from São Paulo.