With several million copies of her picture books in print and a new title out almost every year, Jan Brett has a well-established place on the bedtime-story shelf. In books like The Mitten and The Hat, her watercolor-and-gouache paintings often dwell on the sparkling eyes and soft fur of familiar animals. But The Mermaid, her retelling of “Goldilocks and the Three Bears,” takes place under the sea. Goldilocks becomes a young mermaid named Kiniro who ventures into the home of an octopus family, eating from their shells, sitting on their coral furniture, and trying out their shell-studded beds. Brett spoke with PW about the culture of Okinawa, Pacific tidal pools, and the emotional lives of octopuses.

This is a departure for you, a story set underwater with a new kind of animal life to paint. How do you feel about it now that it’s done?

It’s one of my favorite books ever. The stars aligned and I was really happy about it. Everything just went so well!

How did you decide to set the story under the ocean?

We’ve made many visits to Okinawa, the southernmost islands of Japan, and I just fell in love. My daughter and her husband are in the Marines, and she’s been stationed there three times. She and her family live in a little village right on the ocean. The people are so open and welcoming. Okinawa is part of Japan, but they have their own language, their own culture—at one time, they even had their own kings and queens.

The snorkeling is just beyond belief! The ocean doesn’t get deep very quickly there. You can be walking along chest deep and then there can be a sort of swimming pool with all these amazing forms of sea life. I saw a baby octopus and a lionfish right next to it. It’s like being in another world; it’s absolutely beautiful.

How did the three bears of Goldilocks become octopuses?

Well, at first I thought I would do walruses, because they’re the bears of the ocean. But the Bering Sea is quite stark and not so beautiful. I really wanted to show the sea life of Japan. Octopuses are so intelligent. I loved Sy Montgomery’s book The Soul of an Octopus. She says that there’s a South Asian community that believes that the octopus is the last remnant of a lost race. Which it could be—there’s no fossil record, because except for the beak, they’re all soft tissue. And they only live for a couple of years—even the Giant Pacific octopus only lives for four years.

The hardest thing was to give them human emotions. They can change their skin color, their shape, even the texture of their skin. At the end of the story, when they come home and find everything scattered about and they turn pink because they’re upset, that’s real—they really do turn pink. I love books that give you, not secrets, exactly, but insider information, things that aren’t said but are there in the pictures— that’s what I loved most about Beatrix Potter books when I was a child. The mother octopus has eight fans, and eight teacups. Because she has eight arms.

Did you have to come up with new techniques to paint sea life?

Well, every time I did a fish I had to do research on them. Most of the time when you see paintings of fish, they’re from the side, but from the front they’re a whole different creature; they’re streamlined, swimming, a lot of them are see-through, and there’s a sort of slime element. So I used white pencil over the watercolor. I don’t paint like a traditional watercolorist; if I did it that way, there’d be a whole set of steps I’d go through. I just use the paint like a colored pencil.

It did take a long time. The publisher is always saying, “How many pages do you have done?” There always comes a time when I have to lock down and work on the book because I’m so behind. It’s a magical thing, almost a precarious thing, but when it goes right, the art just unfolds before me as I work. It takes on a life of its own.

The Mermaid by Jan Brett. Putnam, $18.99 Aug. ISBN 978-1-399-17072-0