Hydra (planet)

Hydra was a water-world invaded by the Voord led by Tarlak. The planet was almost entirely covered by water, save for a single land mass: Predora. The First Doctor, Ian Chesterton, Barbara Wright and Susan Foreman helped the native Hydrans defeat the Voord invaders.

The Hydrans were unfamiliar with Earth. (AUDIO: Domain of the Voord)