Percy Jackson and the Olympians: Legends

Her entire body is made out of freshwater and she is dressed in a green-cyan swimsuit made out of fish scales and seaweed. Her blue, watery hair also flows freely.

She loved rivers, springs, and fresh water of any kind. She was very kind, always offered her sibling something to drink, though the others got tired of hearing that the average Titan needs twenty-four large glasses of water a day to stay hydrated. She thought of herself as a nursemaid for the whole world, since all living things need to drink. She is also the mother of Calypso. Tethys was noted to have a very loving and stable marriage to Oceanus, especially when compared to other immortals. This stable relationship of the couple was noted to have positively affected their niece, Hera, who was sent to live with them at their sister Rhea's request to help tame her nasty temper and behavior. Tethys's loving and mostly loyal relationship with her husband had notably caused Hera to yearn for a similar marriage for herself.

Tethys was born as both the youngest daughter and penultimate member of the twelve Titans, the eldest of the three races born to Gaea (Mother Earth) and Ouranos (Father Sky). She, her sisters and her eldest brother Oceanus, all refused to take part in Kronos' usurpation and subsequent castration of Ouranos.