Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are predatory insects that occupy a wide range of freshwater and marine habitats, with some secondary transitions to terrestrial life. They currently represent more than 2100 species distributed through all continents, except for Antarctica, and are especially rich in the Neotropical and Oriental regions. Although the fauna from the former region is relatively well known, some areas remain almost unexplored. Such is the case of French Guiana, where only a few species have been previously recorded, several of which based on collections made in the 19th and early 20th centuries. As a result of material recently collected in the territory, the descriptions of Rhagovelia depressa Rodrigues, Khila & Moreira, sp. nov., R. tantilloides Rodrigues, Khila & Moreira, sp. nov. and Steinovelia vittata Rodrigues, Khila & Moreira, sp. nov. (Veliidae) are presented here. New records for 28 species are also provided, of which Cylindrostethus hungerfordi Drake & Harris, 1934, Neogerris magnus (Kuitert, 1942), Rheumatobates mangrovensis (China, 1943), R. trinitatis (China, 1943), Ovatametra obesa Kenaga, 1942, Telmatometra fusca Kenaga, 1941, T. parva Kenaga, 1941 (Gerridae), Mesovelia amoena Uhler, 1894 (Mesoveliidae), Rhagovelia brunae Magalhães & Moreira, 2016, R. elegans Uhler, 1894, R. ephydros (Drake & Van Doesburg, 1966), R. equatoria D. Polhemus, 1997, R. evidis Bacon, 1948, R. guianana D. Polhemus, 1997, R. tenuipes Champion, 1898, Oiovelia cunucunumana (Drake & Maldonado-Capriles, 1952), Stridulivelia alia (Drake, 1957), S. stridulata (Hungerford, 1929), and S. tersa (Drake & Harris, 1941) (Veliidae) are reported from French Guiana for the first time.