Merpeople are human/fish-hybrids, the legends of which go back more than three thousand years. They're magical creatures of the seas, and the basis for the hit television shows H2O: Just Add Water and Mako: Island of Secrets. According to Sirena, the "real" merpeople are born naturally in the sea.
On special occasions, the Moon Pool reacts to the Full Moon magically and unleashes special effects, such as taking away a merperson's powers, either temporarily or forever, or enhancing a merperson's powers.
Physiology
Cleo, Emma and Rikki as Mermaids
All merpeople share the same basic traits:
When mermaids come into contact with water for ten seconds, they grow a long golden-orange-copper tail and a matching top. Their tails are covered in scales and end in a classic dolphin-shaped fluke. They also have a short dorsal fin running along the backs of their tails from their waists to a little more than halfway down the tail.
Cleo, Rikki and Bella as Mermaids
When mermen come into contact with water for ten seconds, they grow a long ocean-blue tail that ends in a pointy-shaped fluke. They also have a short dorsal fin running along the backs of their tails from their waists to a little more than halfway down the tail.
A merperson's tail is also very strong, this is shown when Emma saves Zane Bennett by smashing in the steel door on Miss Chatham's boat, or when Nixie breaks the frozen surface of the pool in the underwater entrance to the Grotto.
Merpeople also lose their clothes they're wearing in human form which only reappear when they become human again. Their hair keeps it's natural length, but any hair-ties, headbands, hair clips or hairspray disappears, along with their clothes. When they dry, their hair returns to whatever hairdo it was in. Moon Rings accompany the merperson's transformation, i.e, if they have a human form and transform, the moon ring is still there and vice versa, indicating that the ring is a magical object.
The transformation also occurs when merpeople are exposed to snow or ice, but since southern merpeople never interact with snow, they will also develop snow rash and become feverish. Just a only drop can change them. The only way to cure them is by applying dried seahorse powder onto their skin.
It is still unknown how born mermaids reproduce, since mermen haven't been seen for thousands of years by the mermaids, due to the mermen living on land after the great war that happened between them. While merpeople appear mostly mammalian in nature, young mermaids are often called hatchlings, implying that born mermaids lay eggs like fish and turtles. It is possible that mermen have children with humans. If this is true, the genes of merpeople must be very strong for Erik to have been born with powers.
The differences between mermaids and mermen suggests that the two creatures may be a bit more distant than the men and women of the human race or are a separate subspecies, but they are close enough to be considered two sides of the same species.
Psychology
Although considered as the same creature, mermaids and mermen have different behaviors. Originally, both mermaids and mermen lived in groups or pods, but after the great war that happened between mermaids and mermen, mermen no longer lived in pods in the sea. Instead, they were brought up and raised on land. Most likely to hide from the mermaids after losing the war to them, which explains why the mermaids mentioned that mermen haven't been seen for a while. They are described as solitary and territorial. They are also described as power-hungry by the mermaids, and would do anything to obtain power. Zac does not really have this typical mermen behavior, but upon seeing the trident for the first time, he becomes obsessed with obtaining it. He also believes that he is destined to possess it after he falls into a moon spell but then snaps right out of it the moment he touches the trident for the first time. Unfortunately, after being betrayed by the mermaids, Zac comes to see them as corrupt, trouble-making, selfish, devious, and power hungry. He doubles his efforts to get the trident and denounces the mermaids as his enemies, vowing to claim vengeance on them for all the trouble they caused him. Later, as the mermaids make many unsuccessful attempts to strip Zac of the trident, he even goes so far as to try take Mako from the mermaids after he mistakenly believes that they are calling in reinforcements to attack him for the trident. All of this causes Zac to inadvertently recreate the war between mermaids and mermen and nearly finish the job the mermen of the past began.
Mermaids, on the other hand, are determined to learn more about their powers and to master the control of it, instead of gaining more. They even have Mermaid School, which teaches their young how to use their powers and using it wisely to protect and guard the sea, Mako Island, and the moon pool. They live in pods and are never alone, and aren't really as solitary as mermen (although Lyla is considered as a loner, but isn't that solitary and cooperates with the other two). Mermaids usually travel with or hang around in groups of at least two or three people.
Mermaids fear humans as they believe land people will hunt them if they discover they exist. Many mermaid laws forbid ever going near land people or their homes and mermaids who married humans were banished from the pod. The relationship between mermaids and humans was much worse hundreds of years ago. Ancient mermaids would use their siren songs to enchant humans and lure them to a watery grave to preserve the mermaids' secrets. They may have also used storms to sink ships who spotted them or wandered to near the pod's home. Such methods are now forbidden. Mermaids also had an ancient game similar to tug-of-war. A mermaid must use whatever power she has to drive a ship to her side. Ancient mermaids may have used real ships long ago but like the siren songs, using real ships was probably forbidden. In "Battlelines", when Rita asked what to do if a mermaid's invisibility fails to hide her from humans, Nixie replies that they "drown them," reinforcing the fact that mermaids may not care about humans. However, this view is not shared by all mermaids and some may be fascinated by the land and its people. Mermaids will also help humans like summoning gusts of wind for stranded sailors and will even fall in love with humans like Sirena, Mimmi and Rita.
Both mermaids and mermen live on a diet of seafood. They will eat any kind of seafood, such as crabs, lobsters, prawns, tuna, and salmon no matter how it is cooked. In fact, natural merpeople don't like to eat land foods, such as pancakes, instead finding crustaceans, fish, and seafood more appealing to their tastes.
Born mermaids are very naïve about the human world, human terminology, and human technology when they first come to land. This causes them to sometimes stand out in the crowd and draw attention to themselves. When they first get legs, they have difficulty on walking but get used to it after lots of practice. Mermaids are also instinctively terrified of cats. However, they can learn to cope with this fear and conquer this fear like Rita who loves her own feline, Poseidon. Sirena also shows affection to Rita's beloved pet but her friends, Ondina and Nixie, though they no longer fear cats, they continue to dislike Poseidon.
On their birthdays, mermaids give gifts rather than receive them. Mermaids lack any form of currency and they do not build dwellings. Instead they sleep under the stars. How mermaids raise their hatchlings is a complete mystery. Mimmi was raised by her mother until the latter's disappearance. Aquata and Sirena are sisters but never mentioned anything about other family members like a mother while Ondina, Nixie and Lyla have never mentioned anything about blood relatives. To mermaids, the pod is family and they take it upon themselves to raise young mermaids, even if they do not share any biological relations. Pods will even accept and raise mermaids from other pods like Mimmi.
According to Ondina, mermaids share the secret that binds them together, and that mermaids who are in the same pod felt like sisters towards one another. This statement was confirmed as Nixie and Lyla stated that Sirena was like a sister to them. This method also had convinced Rikki to give Weilan and Ondina the Jiao Long Bracelet.
Pods
Main article: Pods
Mako Pod
As revealed in Mako: Island of Secrets, there are Pods of natural-born mermaids all around the world. The Mako Island pod consists of over a hundred. When the moon is full, natural mermaids all around the world honor the moon with a ceremony. Natural-born mermaids live on a seafood diet and wear seashells and similar items as jewelry. The mermaid council, with Veridia as head of the council, make the laws and rules for the Mako Pod to follow. According to Mimmi, the northern pod knows the best spells and potions.
It is forbidden to associate with land people and it is especially forbidden to use a Moon Ring to go onto land.
It is forbidden to let land people come onto Mako Island during a full moon, and it is even more forbidden to let them into the moon pool.
It is forbidden to fall in love with a land person.
It is forbidden to travel too close to land.
It is forbidden to reveal your powers to humans.
However, after Zac saves all mermaids from being destroyed by the merman chamber in "The Chosen One", Veridia begins to show some leniency towards the laws regarding land people, as she now sees that it is possible for mermen and mermaids to live peacefully and that some land people can be trusted with the knowledge of the existence of merpeople. Mermaids are even being taught to walk on land and to forge a connection with the land world.
Sirena, Lyla and Nixie broke the rule of not letting land people on to the island and were later blamed when the pod found out that Zac had fallen into the Moon Pool on a full moon while they were supposed to be guarding it. They were then cast out of the pod. They broke the rules of using the Moon Ring to go onto land to reverse Zac's transformation and also later sang the Enchantment Song, hoping to put Zac under their control in order to try once again to remove his powers.
Rita teaching the girls
Mermaids of the pod use the full moon as a source of magic and power. They create moon rings out of blue moonstone and use them to accomplish many feats and spells, as the rings can heal injuries but can also cause destruction.
Young mermaids in the pod must go through training to be worthy of these rings. Mermaid School teaches them to use their powers correctly and to be sensible in the difficult choices made through mermaid life.
Rita Santos is a teacher on land, at Suncoast High, but possibly could have been a mermaid teacher when she lived in the pod. She helped Lyla, Sirena and Nixie complete their training and gave them their own Moon Rings. By the end of season three Rita had become a teacher for the pod full time. Ondina had became a part time teacher in season three as well and Rita returns to become a teacher later in the season.
Mermen are brought up on land in foster families, go to land school and mingle with humans. Mermen do not have moon rings.
The Mako Island Pod fled Mako in, "Outcasts" and joined another pod in the South Pacific. Once Mako Island was safe again, they returned in "The Chosen One".
Mermaid Council
It is still a mystery how the H2O: Just Add Water characters didn't happen to come across the pod during their period of time living on the Gold Coast and going to the Moon Pool regularly, let alone notice Lyla, Sirena, Nixie who live in the Moon Pool. The only theory fans can think of is that the events of H2O and Mako Mermaids happened in different time periods. It is possible that the H2O characters left the Gold Coast to lead separate lives and become adults before the Pod came to live at Mako. The only piece of evidence of this is that: the moon pool had changed as implied by Rikki, that she and her friends had rebuilt the moon pool. Then it was made into a home by the mermaids, becoming a sacred place.
It is possible that the place where the merperson's transformation happened affects the powers over water, e.g. the Moon Pool at Mako Island gave the people the power to control, freeze and boil water, but the pool in the Sea Caves of Ireland where Bella changed gave her the power to turn water into a jelly-like substance and to turn water into a substance similar to crystal or glass.
Natural Merpeople Abilities
These are natural abilities that all merpeople are shown to have, which stem from their own physiology and are not magical in nature.
Underwater Breathing - Merpeople can stay submerged for long periods of time but they still need to breathe air. Merpeople can hold their breath for at least 12 hours before needing to resurface but with more practice merpeople can stay under for much longer. When mermaids remain breathless, they do not die, unlike humans. They "sleep" underwater, and just awaken when they breathe air again. They can only hold their breath in mer-form. When merpeople are infected with Fish Fever, they undergo changes and develop gills. It is possible that during this time, they can actually breathe underwater.
Limited Transformation - When a merperson is completely dry, their tails transform into human legs. Just a one drop can change them into their mer-forms. Ten seconds after touching water, they will revert back to their true forms. All clothing, including tops, accessories and watches are absorbed by the merperson and vanish during their transformation. Only moon rings remain in both forms as they are magical themselves. Humans who have changed into merpeople possess this power since their first transformation. Since natural merpeople do not have a human form, they can cast a spell to give them legs with the Full Moon or Moon Rings.
Slightly enhanced senses - Mermaids may have slightly enhanced senses suited to life underwater due to living in the sea. To mermaids, land people smell horrible, even the average hygienic human emits this smell but only mermaids can detect it. However, they can get used to the smell. By smelling Rita's supply of squid ink, Lyla could identify where the species of squid came from. According to Lyla, as mermaids are connected to the sea, they can sense a change in the currents, whether a shark is dangerous or if a dolphin will help them find their way home. In H2O: Mermaid Adventures, mermaids have the same range of hearing as dolphins. With this sound they can hear things humans cannot but their human half allows them to hear sounds cetaceans can't.
Durability - Merpeople can swim for days without fatigue. Mermaids are also able to swim at 600 km per hour for long periods of time, something which no human has the endurance to do. However, they only appear to have this ability in mermaid form.
Speed-Swimming - In water, merpeople also have the additional ability of Speed-Swimming. When a merperson speed-swims their body is enveloped in bubbles that they use as a jet stream to swim quickly. This can be a great advantage when trying to flee from enemies such as another mermaid/merman or boats and other water crafts. It has also been referred to as, "torpedoing."
Aquatic adaptation - Merpeople can adapt and swim in both fresh and saltwater but they prefer to live in saltwater. Depending on where they are born, mermaids may be resistant to certain elements in that area. Northern mermaids may be resistant to low temperature as they swim in cold waters like the seas around Canada the arctic circle. The Canadian Mermaid wasn't suffering from the cold or hypothermia, even though she was swimming in an area where the temperature was very low and the humans she attacked were dressed in thick clothing to keep warm, further implying the low temperature and Northern mermaid cold resistance.
Zoolingualism - Natural-born merpeople have the unique ability to comprehend and speak the language of sea creatures (for instance, dolphins and whales). It is unknown if the ability can be learned, but it is unlikely. Nixie, Sirena and Rita are known for demonstrating this ability with dolphins, while Mimmi also speaks dolphin, humpback and blue whale. In H2O: Mermaid Adventures, the main characters gain the ability to speak with all sea creatures, including cetaceans, cephalopods, fish, marine reptiles and crustaceans.
Merpeople have a natural gift for spell making using ingredients found in nature. They make potions to perform things their magic powers cannot like heal wounds, transform animals, grant wishes and neutralize anything, including other spells.
Lewis McCartney found a book, "Mermaid Mythology" that held a recipe for a Mermaid's Potion that could give mermaids the power to grant wishes. It may have possessed more potions like the wish-granting spell.
Moon rings are a huge part of mermaid magic and every mermaid is taught how to use one and all receive a ring after they finish mermaid school. Moon rings are a vital part of a mermaid's survival as merpeople use them for healing what potions cannot, enhance the natural world for camouflage, grant them human form, and amplify their inherent magical powers. With their rings, mermaids can cast many spells. Mermaids can also craft other magical items like the bracelet of Jiao Long. This has red stones, implying mermaids have altered the magic of the stones for a specific purpose. Rita mentions that only a mermaid can wear the bracelet.
Weaknesses
Sirena and Lyla with Snow Rash
Snow Rash - Natural merpeople such as Lyla, Nixie, Sirena and Ondina that were born in Southern oceans, have never interacted with snow. If they do end up going into contact with it, it will make them develop Snow Rash, a moss-green rash caused by contact with snow. It is accompanied by itch, fever, and malaise and doctors such as Dr. Blakely couldn't realize what it was. Snow rash interferes with their powers and prevents them from using hydro-thermokinesis and pyrokinesis to warm themselves. A mermaid who tries to use these powers will only generate cold and lower the temperature. It is not known whether a human transformed into a merperson by a Moon Pool also develops the disease. It was first shown in Mako Mermaids. It seems to be very fatal to Southern Mermaids. It is also likely that merpeople born and raised in icy waters develop some immunity to the cold and also on Snow Rash. The only way to cure this allergy is a Dried Seahorse Powder that Rita contains stored within a silver seahorse. To heal, the dust must be sprinkled on the affected part of the skin, and it will immediately disappear.
Dangerous Coral
Fish Fever - A strange, rainbow-colored coral houses a poison that affects both fishes and merpeople. It causes them to be overexcited, but the more the poison seeps into their system, the more ravenous they get. The poison also causes a tremendous mutation in a mermaid's physical form. For Emma: her copper-golden-orange scales turned white and scales even appeared on the skin, her hands became webbed, her nails turned black and later into claws, her skin became more monstrous; her neck sprouted a set of gills, her hair started to turn green, her eyes turned yellow, and she made monster-like noises. She also developed a desire to be wet. Emma was later cured when Lewis sprayed an antidote on her skin, which was developed by Laurie. When a fish affected by coral's poison, its scales will turn white, and they will develop a out of control hunger. Laurie said that if Cleo's fish was not cured in time, he would have died. The same goes for the merpeople.
Ambergris
Ambergris - Is an old substance that at one point in time was used to make beauty products such as ladies perfume. It comes from the intestines of a whale and it can be used to attract mermaids. In "Irresistible", Zane Bennett finds some old ambergris which Nate later tries on. The smell from the ambergris makes him stink but it also makes him literally irresistible to Cleo, Emma and Rikki. Ambergris was also one of the ingredients used in Mimmi's potion of fifty moons to remove Zac's powers.
Allergic Reaction - Mermaids seem to have an allergic reaction to a certain substance of aftershave, which cause their powers to blow uncontrollably when they sneeze. Mermaids also had an allergic reaction to a formula Lewis created to allow mermaids to get wet while in human form, and not grow tails. The allergic reaction however only manifested as red spots all over their bodies when mermaids were in their human form. Besides this, Lyla, upon being asked by Dr. Blakely of what sort of allergies she has, she calmly responds with: "Only kelp spores in the Atlantic."
Sickness - Merpeople don't get sick, unlike humans. However, they can be infected if they come across a sick land dweller and can spread it to other merpeople as well. The symptoms involve oozing heat from out of their bodies and breathe fire whenever they sneeze. Rita Santos invented a remedy for such situations after coming across such occasions multiple times. Mimmi, being inexperienced with such situations, tried to concoct a potion, but it only worked temporarily, after which the sick merpeople will feel cold and eventually breathe ice in their sneezes.
Dehydration - As sea creatures, merpeople require water to remain healthy. Mermaids have been known to die from drying out. Though magically assuming a human form extends their time on land, they still cannot stay on land forever. Merpeople can die from water deprivation. As mentioned by Sirena, merpeople have died from, "drying out". It is unknown if a human transformed by a Moon Pool would also have this effect as well or suffer from this weakness.
Trivia
Natural-born merpeople do not have a human form, although they have the ability to give themselves one. Since that kind of magic isn't possible without a powerful source of moonlight, this can only be done with a Moon Ring or full moonlight itself. When natural-born merpeople first grow legs, they are naked. They also have difficulty getting used to walking at first but with lots of practice, becomes a habit.
Merpeople, even humans that were transformed into one, feel much better in the water than on the land.
It is possible that the amount of time it takes for the transformation to take full-effect can vary depending on the amount of water the merperson came into contact with. For example, if a bucket of water was dumped on a merperson's head or they dove into the ocean, they'd transform immediately. If a merperson came into contact with a normal amount of water (such as spilling a glass of water on oneself), it would take the normal 10 seconds approx. However, just a drop can change them.
Water is much more than a mermaid's home. Water can help heal or revive them. However, this only applies to certain illnesses or injuries as it takes more than water to heal a mermaid who is struck by the Moon Ring or the power of the trident. Mermaids who stay in the sea don't get sick.
Merpeople are mortals, like humans.
All natural born merpeople have a strong instinct to eat seafood. Humans who were transformed by the Moon Pool do not experience this, apart from when they are under the Moon Spell (which makes them behave like they are real merpeople).
It was revealed in Dolphin Tale that natural-born merpeople can speak the languages of sea creatures, as Sirena and Nixie can speak dolphin and Mimmi can speak dolphin, northern penguin, and humpback whale.
It is possible that only natural merpeople can make themselves invisible.
Merpeople, including natural ones, are said to have a hard time controlling the power of the full moon when they haven't been properly trained. For this reason, they need to learn to concentrate on letting the moon's magic flow through their bodies rather than resist it. After this, they can wander out in the moonlight.
The full moon's effects on merpeople may be a reference to the mermaids in Peter Pan by J.M. Barrie. In Barrie's story, the mermaids experience a "haunting" change at the "turn of the moon."
The dangerous reputation of the Northern pod may have been inspired by the legends of dangerous, wicked mermaids which are most common in the Northern hemisphere.
It is unknown how mermen reproduce, but they may marry human women. This would explain their land form since natural mermaids need a spell to gain human legs.
Zac may be the only full merman in the twenty-first century as he was born the same way as a mermaid.
Mermaids and mermen are warm blooded creatures and are able to be seen invisible by heat detecting equipment.
Mermaids have great knowledge of the underwater world and know things that marine biologists are unaware of. Their knowledge is limited to the creatures of their oceans. Mimmi was unaware that penguins are only native to the southern hemisphere.
A few known natural predators of mermaids are orcas and giant squids. Rita uses these as examples of why a mermaid would require a certain power if she ever came across them.
Just like in the legends, natural mermaids have a slight streak of vanity and often comb their hair like the classic depictions of mermaids.
