Aguatunisian

Riva, the ship's comms officer, introduces themself in the first episode and sits in a glass sphere of water on the bridge SOE1·00:06:55. Riva's character art describes a nonbinary character from an aquatic alien species with fins, scales and webbed hands SOE1·00:07:09. Riva says their real Aguatunisian name is an image of finding a current underwater, too complicated for most non-psychic life forms SOE1·00:07:09.

Aguatunisian is Riva's aquatic, psychic species SOE1·00:07:09. In the second episode Brennan describes the species as one where breeding is very hard, and as one where thousands of babies are born at once from a clutch and raised communally SOE2·00:58:49. Riva also corrects a crewmate who calls them a fish: "Not a fish, Aguatunisian" SOE2·00:57:56.

At Fantanimalland the crew see Aguatunisians presented as an exhibit, and Brennan calls them a "fully sentient species of alien" SOE10·02:15:10. Riva later jokes about what their fins looked like at a young age SOE12·00:48:20. Riva says that for their species it takes "five people who all have to be madly in love with each other", and "I'm one of 10,000" SOE12·01:06:45 SOE12·01:07:07.