"Ponyo" dispenses with Andersen's signature dour, Victorian Protestant hopelessness, which infused the original "Little Mermaid," and the animation is divorced from the Disney version by its lack of calypso music and seashell bras, among other things. If "Ponyo" carries any message, it's the "don't dump stuff in the ocean" environmental angle one might expect, although it's mild enough that it doesn't distract from the general action.
In fact, Miyazaki more or less ignores the sort of proselytizing typical of fairy tales in general. The implied message seems to be that defeatism is the only real danger, and that renewal " both of the physical realm and of the spirit " is always possible, maybe even inevitable.
As usual, Miyazaki's animation is visually stunning, particularly the sequences when Ponyo is looking for Sosuke, and those including her goddess mother. He creates a slightly stylized ocean that infuses every scene and dictates their moods, acting as a character in its own right. The profusion of fish, eels, jellyfish, crabs and every other type of sea life you can think of is amazing, with each piece perfectly rendered and synchronized across the screen.
"Ponyo" is another great example of what Miyazaki does best: creating a sense of adventure for children, while reminding adults what it felt like to be a child. At 100 minutes, it's short enough for most kids to make it through, but long and gorgeous enough to satisfy their grown-up keepers.