Zac, a teenage boy, decides to camp on Mako Island, unaware that three mermaids, Lyla, Nixie, and Sirena, guardians of the island, are watching him. That night, when the full moon rises, the boy comes into contact with the magic water of the Moon Pool. The following morning, Zac discovers that he has the ability to control and manipulate water. Later, after accidentally falling into the water, he finds that he has also become a merman with a fish-like tail. His new-found merman abilities threaten to expose the existence of merpeople. After being cast out by their pod for allowing Zac to visit the island, the three mermaids, curious about living on land and motivated to remove Zac's powers, venture onto the land and learn to live among humans.
In series 2, the mermaids continue to discover Mako's secrets and learn more about the merman chamber. While Lyla and Nixie go in search of a new home, Sirena is left with Ondina and Mimmi, new mermaids who continue the effort to remove Zac's powers and reclaim the island for their pod. Evie, Zac's girlfriend, faces her own battles when she becomes a mermaid herself, and the others try to help her cope with the change. They also discover that Zac is a born merman and is Mimmi's brother.
In series 3, with Sirena away in Hawaii with her sister Aquata, Zac, Ondina and Mimmi are joined by Weilan, an Eastern mermaid who has fled to Mako for sanctuary from a magical water dragon. The mermaids discover that the dragon is Zac and Mimmi's long lost mother and must find a way to save her.
Lucy Fry as Lyla (series 1), seen as the leader of the three mermaids. She is hot-headed, determined, but still very smart. Despite initially only being interested in him for the sake of removing his powers, she develops an attachment to Zac. She has left with Nixie to search for a new home for the pod in season 2.
Ivy Latimer as Nixie (series 1), one of the three mermaids. She is an adventurous girl, who often gets into trouble and only does what she believes is right. In series 2, it is explained that she has left with Lyla to search for a new home for the mermaid pod.
Amy Ruffle as Sirena (series 1–2), one of the three mermaids. Naive and sweet, she acts as a mediator and peacemaker when Lyla and Nixie quarrel.
Chai Romruen as Zac, who becomes a merman after falling into the Moon Pool during a full moon while camping on Mako Island. He grew up surfing and is sporty. In series 2, he discovers that he was born a merman and that Mimmi is his sister.
Isabel Durant as Ondina (series 2–3),[4][5] a mermaid who works to remove Zac's powers. She is headstrong and tries to do things her way.
Allie Bertram as Mimmi (series 2–3),[4][5] a mermaid who works to remove Zac's powers. She is intelligent and inquisitive, and occasionally has to bail Ondina out of trouble. She eventually finds out that Zac is her long lost brother.
Gemma Forsyth as Evie (recurring, series 1; main, series 2–3), who is Zac's girlfriend. In series one, she believes the girls are stalking her and is jealous of Zac spending time with Lyla. She eventually learns the girls are mermaids and apologises for her quick judgement. She is accidentally transformed into a mermaid in series two and back into a land girl again in series three.
Alex Cubis as Erik (series 2),[4] a merman who is descended from a line of mermen who have not been seen for thousands of years. He is solitary and elusive. Erik is a waiter at Ocean Cafe with Carly.
Linda Ngo as Weilan (series 3),[5] a Chinese mermaid who accidentally leads a magic water dragon to Mako. She is sassy and has a dry wit. She prefers sleeping and socialising on land as the dragon has caused her to be wary of life in the ocean.
Dominic Deutscher as Cam, Zac's best friend who quickly becomes aware of Zac's transformation into a merman. While Cam is initially supportive of his friend and helps to keep his secret, he becomes jealous and envious of Zac's powers. He is outraged when Zac tries to return the trident to its chamber, and works to become a merman himself. They later make up and Cam helps Zac destroy the merman chamber.
Kerith Atkinson as Rita, the school principal and a mermaid. She left her pod years ago to be with a human boy she fell in love with, but who died before they could marry. She serves as a source of knowledge and history for the girls, and teaches them how to properly use their powers.
Rowan Hills as David, an employee at the Ocean Cafe. He and Sirena become mutual love interests. David finds out about mermaids at the end of series 2.
Brooke Lee as Carly, an employee at the Ocean Cafe. She had feelings for David but is now with Cam. She is also Evie's best friend, and later finds out about merpeople in series 2.
The show, announced in July 2011,[6] consists of 26 episodes of 26 minutes each, plus an option for one 90-minute episode.[7][8] Filming was to begin in April 2012,[9] but it was postponed to the beginning of May.[7] On 8 May 2012, Shiff Productions announced the principal cast and the start of the shoot.[7][10] Filming ran through 12 October 2012.[11]Mako was scheduled to broadcast in the second half of 2013,[12] with a second series confirmed before the first had screened.[13] Production of the first series totalled A$12.3 million.[14]
The show was first announced as Mako: Island of Secrets, then as Secret of Mako Island, and finally as Mako Mermaids for its international release.[15] It debuted domestically on Network TenasMako: Island of Secrets on 26 July 2013.[16]
In partnership with Shiff Productions, Netflix is the exclusive internet television provider for the series. The first thirteen episodes were released on 26 July 2013, with the second half of the season airing on 15 September 2013.[17][18]
On 8 November 2013, broadcasts of the show were switched from Network Ten to the free-to-air digital channel Eleven, first airing on Friday mornings at 8:00 a.m. and later changed to Sunday mornings at 11:00 a.m.
A second series was confirmed in February 2013, with production beginning in the second half of 2013 contingent on funding from Screen Australia.[19] The first half of series two premiered on Netflix on 13 February 2015 in North and Latin America, United Kingdom, and other territories.[20] In Australia, the second series screened on Eleven Sunday mornings at 10:00 a.m. from 15 February 2015. The second half of the series was released on Netflix on 29 May 2015.[21] Netflix labelled the first half as series two, while the second half was called series three.
A third series of 16 episodes was announced in 2014,[22] began screening on Eleven on 15 May 2016 and was released on Netflix on 27 May 2016.[23] The series introduced Chinese mermaid Weilan (Linda Ngo),[24] and featured the special guest appearance of Cariba Heine as Rikki Chadwick in the final two episodes.[5]
A movie was planned to be produced after the series ended. However, the plan has been put on hold indefinitely.[25]
Series 3 is listed under Season 4 on Netflix, as Netflix released Series 2 in two separate parts in 2015.
