The mermaid government is the organization that runs merkind. Its description and actions in various mermaid shows is very contradictory and ambiguous.
Mermaid Government[]
A blue-cloaked member of the government appeared when Justin asked, and gave him a potion to keep him from popping a tail when wet.
The Mermaid Government was also an ally (and sometimes enemy) of a young mermaid named Caroline. They sent the original potion to Caroline, along with a series of notes and potions to undo David’s tail, even threatening to take her powers away if she didn’t make him human again. Their main face was an agent “whose name is not important” who first showed up to tell Caroline that she’d impressed them enough to let the siblings keep their powers. They later sent her on a mission to destroy all Sirens, though she decided instead to turn them all into mermaids.
After Chloe and Stacy showed off their powers in public, they got a summons from the government. As instructed they got into their pool and were transported to a different pool, where they were informed that they were no longer worthy of powers or tails. The girls didn't seem that upset, but then again they were able to wish their tails right back a little while later.
Mermaid Guardians[]
The Mermaid Guardians were a group of mysterious figures who claimed to be “everyone’s guardians.” A few years after a mermaid was kidnapped by someone named Roxy, they contacted her daughter Ashley, sending her a necklace and a series of notes. When that only confused her they contacted her directly as disembodied voices, telling her to get the Book of Mermaids her mother had given her when she was little to understand the powers she would need to defeat Roxy. Later they told her they’d be sending a girl named Lexi to help her out, and that she needed to eat the Water Plant to gain Hydrokinesis. They also provide her with a potion to keep Roxy from touching her before she sets out to confront her mother’s kidnapper.
Mermaid Deities[]
Jordan[]
Listed in the credits as "Leila as Jordan."
This goddess appeared to Peyton and Maddy, along with her (admittedly fake) dolphin Squeaky. She could magically change other people's clothes with a snap of her fingers and freeze time for particular people. The reason she showed up was to talk about Peyton's upcoming move to Oklahoma. Not only had Peyton not mentioned this to her friend, but the Mermaid Council was considering taking away her powers. There were a lot of bad mermaids in Oklahoma. She didn't agree with them but it wasn't her decision. Instead she suggested that Peyton train with her powers to prove herself to them. After a round of testing Peyton's reactions and abilities, the goddess called the Mermaid Council and they reversed their decision. The trio shared a group hug.
The Mermaid Council(s)[]
The Council sent Destiny to train Ashley, then rescue her when she got stuck in the past.
They were also reluctant to let Peyton move to Oklahoma, an area with a lot of evil mermaids, and planned to take away her powers. However with help from the Goddess, she was able to train and convinced them to let her stay as she was.
Thexie's father was a scribe employed by the Mermaid Council, and when she became queen Nori was required to join their regular meetings.
Mermaid Kings[]
King Neptune[]
Neptune, sometimes referred to as Poseidon or Triton in dialogue, selected Lexi and Sofia to serve him and his queen as full-time mermaids, summoning them to Atlantis with a letter. They were meant to meet at the beach, but when he arrived they were hiding. Furious, he cursed them, but gave them the chance to regain their powers if they found a pair of rings. They succeeded and got their powers back.
Some time later, after the girls made "the bond of true, unbreakable friendship," he sent them a message to inform them that they now had Mer-marks, the mark of a true mermaid, and had reached "Level 2." Now their tails and powers were only vulnerable to someone with power equivalent to the king. There would be some weird side effects, but they wouldn't last.
King Triton[]
According to Sapphire’s research, he decided he needed to make more mermaids he could trust, since there were only a few left in the world. Hence sending her a necklace and instructions to turn her into a mermaid.
Mermaid Queens[]
Abby was apparently the half-human daughter of the Queen of the Mermaids.
A young mermaid named Alison was contacted by the Queen, who gave her advice about her powers and tail regularly.
The Queen let Dasia know that three powers were the norm for mermaids, but a full mermaid needed to have ten.
Cleo's Grandmother[]
A young mermaid named Cleo found out that she was the granddaughter of the dead Queen of the Mermaids, one who had been killed by the Siren.
Queen Nara[]
Nara was the queen of the Nereid clan of mermaids, one of the largest and most advanced mermaid clans. As a royal Nereid she had a shimmering blue tail. She died in 2001 shortly after the birth of her daughter, who was separated from her by the storm that presumably killed her. She also had a niece, who was second in line for the throne after the princess.
Queen of Neptune[]
The mermaids of the planet Neptune had a Queen of their own.
Queen of the Sea[]
She sent Logan a necklace to give her powers, and “bears” (cherry-flavored gummy bears, essentially) to keep her tail healthy.
Mermaid Police[]
The Mermaid Police were sent after Amelia for unknown reasons.
Mermaid Princesses[]
Princess Alicia[]
Alicia was a princess of the Undersea realm, and implied to be the daughter of the current Mermaid Queen.
Princess Ashlyn[]
Ashlyn was the princess of the Southern Kingdoms. She was raised as a mermaid until something bad happened--she wasn't sure as her memory was faulty--and she wound up on land.
Princess Jewel[]
Jewel was born a mermaid princess (and her twin brother Rin a prince) but they were kidnapped as infants and raised by humans, thanks to the work of a shapeshifter who wanted their powers. Jewel had the power of fire.
Princess Rowena[]
Rowena was born a mermaid princess, and in her early teens the Mermaid Council summoned her and named her their leader. Because of this she was targeted by a Siren and had to go into hiding.
Princess Nori[]
Nori was born to Queen Nara in 2001, inheriting her shimmering blue tail and the throne of the Nereid clan. She was lost in a storm while she was still a baby, and was raised by humans until she turned thirteen. Although she was aware of her mermaid heritage, she didn't find out she was a princess until her friend Thexie put two and two together. As the queen, she was able to live wherever she wanted, so long as she attended meetings of the Mermaid Council.