Tethys is a water Titaness, she is shown having a blue body composed of water, long white hair and webbed hands: she is the most humanoid of the featured titans in her original form.
Her form is later altered by Hera to appear to be made completely of water and ice (so that physical attacks do her no harm), have a mermaid like fin that sprouts into octopus tentacles instead of legs and a more purple color as opposed to her original blue.
She is shown to be the only one of the Titans to accept her new form right away, smiling after examining her new-found powers. She meets her end when Iolaus tricks her into running into Mnemosyne, causing her to steam dramatically: a moment later, they both to fall into Tartarus.
- Tethys was voiced by Alison Wall.
- Tethys is never named aloud in the film: her name is mentioned in the credits only.
- Of the Titans featured in the movie, Tethys is the only one to be associated with the relevant element in mythology - she is a Titaness associated with the seas, the consort of Oceanus. The elemental associations of the other titans are unique to the series.
- According to Homer, Tethys and Oceanus were on good terms with the Olympians by the time of the Trojan War. Hera referred to her as "the mother" and told Zeus that she would recuse herself from the War by visiting her.