Rita was born to an unnamed mermaid in the Mako Pod in late 1970s. During her childhood, she met another hatchling named Veridia, and the two quickly became best-friends. Rita began attending Mermaid School in the Mako Pod, and eventually she graduated and received her own Moon Ring. One day, she met and fell in love with a human named Harry. Knowing their love was strictly forbidden by mermaid laws, Rita casted the Legs Spell on herself and eventually the Mermaid Council realized what she was doing, and who she met. Her best-friend, Veridia, became the head of the Mermaid Council, and furious, she had no choice and banished Rita, breaking their friendship. She left her pod, and began to live in land with Harry, who was already her fiancé. Before their marriage, Harry tragically passed away, leaving Rita alone. At some point before or after his death, Rita had a pet cat named Poseidon, who became her new best-friend. Rita eventually became a teacher in Suncoast High, and later, she became the principal. Despite this, Rita promised herself to never return to her pod, a decision she ultimately breaks many years later.
Although Harry passed away, Rita has been successful on land and was the principal of the local high school. She has survived and protected her true identity by keeping a somewhat cool and distant outer image.
Although a bit lonely sometimes, Rita has more or less adapted to her life.
That is until three young mermaids turn up and ask for help. Rita is torn- she gave up mermaid life, and she doesn't want three reckless young mermaids blowing her cover, but Rita can't turn them away. As she becomes their mermaid mentor and guide, Rita discovers that although there are complications, the mermaids bring companionship and laughter back into her life. Though she truly loved being a mermaid, she still refused Lyla's offer to return home and become one of the pod again, stating that her life now was on land.
Rita's usual role is to provide knowledge and wisdom on magic whenever the merpeople need it and does not usually get involved in their adventures. The one exception is in "Reunion" when her ex friend at the time Verida, reveals her intentions to deal with Zac personally when she learns he has unlocked a merman chamber. Fearing for Zac's life, Rita follows her and threatens Veridia with her own powers when she nearly attacks Zac. Rita and Veridia make amends after Veridia realizes that Rita was right about Zac being a friend and that some land people can be trusted, even agreeing with her when Rita expresses hope that one day the world of land and sea will become one.
In season 3, Rita quit her job as Principal of Suncoast High and decided to go back to the pod. Now Rita teaches at mermaid school, replacing Ondina in her position while maintaining residence on land.
Rita is a very pretty mermaid with auburn hair and pale eyes. She wears clothes in different colors and she is seen wearing a seahorse necklace. As a mermaid, her hair is let down and she has an orange-scaled tail with a matching orange-scaled top.
Rita possesses the ability to transform into a mermaid ten seconds after direct physical contact with water. She turns back into a human a few minutes after she is out of the water and when the water on her has fully dried. Once her body is completely dry, her human form reverts back to what she appeared to be before her mermaid transformation. As a mermaid, Rita has the ability to swim at a super speed, hold her breath for more than fifteen minutes, and dive at depths no human being is capable of.
Rita has all regular and weather powers, and she displayed the powers of Hydrokinesis, Volume Reduction and Atmokinesis. Rita can speak the language of dolphins, and she is vastly skilled with magic and even invented methods of her own. She also has all the natural abilities a merpeople have, like Invisibility and Invisibility Detection, in which she was the first merpeople to display this ability.
Rita has all the typical weaknesses of a Southern mermaid.
- Rita is a shortened version of the name "Margarita", meaning "pearl" in several languages including Persian, Sanskrit, and Latin.
- She has a pet cat named Poseidon.
- Harry died before they got married as revealed in "Lyla Alone", although it is unknown how Harry died.
- Rita is the only mermaid seen using the power to reveal invisible merpeople.
- Rita wears tortoiseshell jewelry as revealed in "Close Call."
- Rita loves lobster and seafood.
- Rita doesn't want to go back to the pod, however, by the end of season 3 she quits her job and goes back to the pod, while also maintaining her residence on land.
- Rita becomes the teacher of the hatchlings in Mermaid School after Ondina gave up her job.
- Rita was in mermaid school with Veridia and was top of the class.
- Rita wrote a thesis on dolphins.
- It seemed that she and Veridia were very close before Rita left the pod, as stated in the episode "Stay or Go."
- She seemed have made her own potion for mermaids to cure the common cold.
- She is the only mermaid present on the entire show.
- Main article: Rita Santos/Gallery