Thalassa Gilou
Aquaan, Tal's assistant
Gilou is disgusted that the city that has traditionally been governed by her family is in the hands of a human. It's partially her own fault - instead of staying at the Lighthouse and learning governorship, she went to live with her grandparent Zefonith when she was sixteen to study biological sciences. Partasah was both her birth and donor parent ( she's more or less his clone ) but she considers Nephos her father.
First Appearance (child): 007: Drowning VII
First Appearance (adult): 016: Passage IX

Tal Monteblanc
Human, Governor of Port Tethys
Originally from the very restrictive world Veras, Tal was hired by Partasah to govern the city. While he can claim that he rules a planet, he's technically more the overseer of a tourist trap. Even after twenty years, the reserved and inhibited Tal never really managed to adapt to the loose and open Tethyn culture.
First Appearance: 001: Drowning I

Thalassa Nephos Caliga
Human, supersoldier ( retired )
Originally from a commune on Garden, Nephos ended up in the army and eventually the supersoldier program during the war. He followed Partasah back to Tethys and married him. He is perfectly happy to be a pacifist again, spending his days gardening and looking after the Lighthouse and its inhabitants. He is not taking Partasah's death well, to say the least.
First Appearance: 002: Drowning II

Thalassa Partasah
Aquaan, former governor/harbourmaster of Port Tethys
Formerly an anthropologist, Partasah took over governorship of the city from his sibling Alu after the war. Wanting to spend more time with Nephos and Gilou, Partasah hired Tal to take his place as governor, while taking on lighter duties as the city's harbourmaster. He was the black sheep of the Thalassas after a family argument, enough that he refused to go to his parent for help when he developed a condition that made him age too quickly.
First Appearance: 004: Drowning IV

Entomorphs
The natives of Tethys - since they're hunter-gatherers, rarely use tools, and speak in pheromones and buzzing, it took humanity over a decade to realise they were not only sentient, but bright. Entomorphs are generally friendly and curious and have no concept of other people's privacy. They have a firm concept of their own, however, and refuse to let anyone into their territory. Since Tethys is technically theirs, nobody's pushed the issue. The entomorphs treat Port Tethys as a big interesting thing that exists to entertain them, like a permanent fair. The local humans shrug and accept the entomorphs as a part of life.
First Appearance: 002: Drowning II

Anthemys Monteblanc
Human, painter
Tal's younger sister and his primary source of motivation. Her technical skills are impressive but she lacks real creativity. She'll never become famous and doesn't care. Her favourite subject is male nudes.
First Appearance: 008: Passage I

Thalassa Zefonith
Aquaan, one of the founders of Tethys, bioengineer
Due to a family argument, Zefonith was banished to the sea eighty years ago. After Partasah's death, he figured the exile was over. He's one of the more famous Aquaans, being one of their most skilled bioengineers to the point of being considered a miracle worker. He finds humans ridiculous. He is Partasah's birth parent.
First Appearance: 016: Passage IX

Jendolyn Basaday
Human, supersoldier ( retired, ) chief of security
Born on Earth, but raised on Tethys by her grandfather after her parents died. Life took her to a half-dozen different planets as she pursued higher education, got caught up in the war, took up law enforcement, and eventually brought her back to Tethys. Jendolyn comes across as a bit on the apathetic side - she does care, she's just not easily shocked.
First Appearance: 030: Passage XXIII