Vicier said
There's a spin off?
Yes, about 3 mermaid born mermaids who gain legs, instead of the other way around. It is also set on Mako.
Zac is a teenage boy who decides to camp on Mako Island, unaware that three mermaids, Sirena, Nixie (this is where I got my name from), and Lyla, who are 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 will cause problems for the mermaids.
The three mermaids, curious about living on land and motivated to remove Zac's merman powers, venture onto the land and learn to live among humans.
Mako Mermaids IMDB
Mako Mermaids Wiki
I watch it on Netflix.