| Scientific Name | Author | English Name |
|---|---|---|
| Hydra utahensis | Hyman, 1931 | Utah hydra |
| Hydra rutgersensis | Forrest, 1963 | |
| Hydra pseudoligactis | (Hyman, 1931) | False brown hydra |
| Hydra oligactis | Pallas, 1766 | Brown hydra |
| Hydra oregona | Griffin & Peters, 1939 | Oregon hydra |
| Hydra littoralis | Hyman, 1931 | Swiftwater hydra |
| Hydra minima | Forrest, 1963 | |
| Hydra hymanae | Hadley & Forrest, 1949 | Jersey hydra |
| Hydra cauliculata | Hyman, 1938 | |
| Hydra carnea | Agassiz, 1850 | |
| Hydra americana | Hyman, 1929 | White hydra |
| Hydra canadensis | Rowan, 1930 | Alberta hydra |
| Chlorohydra hadleyi | Forrest, 1959 | |
| Chlorohydra viridissima | (Pallas, 1766) | Green hydra |