Already a hit in Japan, Ponyo on the Cliff by the Sea, opened Sunday at the Venice Film Festival, where it is competing for the coveted Golden Lion.
Ponyo tells the story of a goldfish who longs to become a girl after getting a glimpse of the human world when she is rescued from a jam jar by 5-year-old Sosuke, a boy who lives on a cliff above the sea.
As in The Little Mermaid, Ponyo's transformation is opposed by her father, an underwater sorcerer who was once human, and she must make a sacrifice, in this case her magical powers, to become human.
Only true love can guarantee her transformation.
The film draws easy comparisons to The Little Mermaid and Finding Nemo. But unlike The Little Mermaid, Miyazaki's underworld setting is not pristine. And unlike Finding Nemo, he doesn't create an environment that approaches realism.
"The sea is something that is so very complicated. I just thought it would be great to draw it by crayon," Miyazaki told a news conference on Sunday. While he said that digital techniques are useful, they have at times become excessive.
"I think animation at times needs the pencil and needs man's drawing hand," Miyazaki said.
Miyazaki's animation depicts layers of sea life churning one over the other. Waves transform into fish and back again, schools of fish surge as if a wave. Details keep it real and modern: a passing frigate in the background, a knocked-over flowerpot in a storm, a broken piece of ramen noodle on the coffee table.
Miyazaki acknowledged inspiration from the Hans Christian Andersen story, but said the similarity was only glancing. He said he was always bothered even as a child that Andersen's mermaids were deprived of souls.
Ponyo is set in modern-day Japan and Ponyo of course is no mermaid. She is a goldfish, with human face, whose transformation into a girl is evolutionary: first sprouting hands and feet that resemble those of a chicken and become more human as the affection between her and Sosuke grows.
Ponyo is all soul, showing her human side as she clings toddler-like to her first human possessions - a blue bucket, a towel and a lamp - and interacts tenderly with a human infant.
The movie's final message is one of absolute, unconditional love and acceptance. In the closing scene, the 5-year-old Sosuke pledges his love to Ponyo, be she fish, human, or something in between.
Ponyo has been reported to be the 67-year-old Miyazaki's last film, but he suggested other projects were in the works - though that he would rely increasingly on contributions from his staff.
"I am 67 years old, when I do my next work, I'll be more than 70, so I probably will have to have help from the younger generation," said Miyazaki, who took home the lifetime achievement award from Venice in 2005.
In Japan, Ponyo had taken in 11.46 billion yen (US$104 million) from its July 19 opening to Aug. 24, which its distributor said was behind the pace of Miyazaki's Academy Award-winning "Spirited Away," which reportedly took in some 30.4 billion yen (approximately $NZ410 million).
Ponyo is being distributed in the United States by Disney, but no release date has been set. It will begin rolling out in European markets toward the end of the year.