Of course, no review of Nadia can get around a certain arc in the middle. Episodes 23-34 are directed by a replacement director. The twelve "filler" episodes, in my opinion, aren't horrible, but they ARE horribly mediocre in comparison to the rest. For those twelve episodes (episodes 30 and 31 excepted), the plot comes to a stand still. Life on a deserted island simply doesn't compare to the excitement of the main plot. However, that's not actually the worst part of it. I wouldn't have minded so much if it hadn't also distorted the characterization to a nigh-insulting level. More on that later.
So would you be better off skipping the island and Africa arcs? While they have their moments, in my opinion, the answer is yes. The experience would probably be enhanced if you left them out. The director felt only episodes worth keeping from those twelve were 30 and 31 and I'm inclined to agree. Those two are good and should be watched. You won't lose anything by watching the rest unless you're remarkably touchy, but you won't really gain anything either.
Art: Yoshiyuki Sadamoto's character designs are as nice as ever, and the animation is generally good. Emotions are portrayed nicely and the complicated technological wonders and battles are quite nuanced and pretty. However, the series IS 20 years old and looking its age.
As for the supposed iffishness in part of the animation during the filler arc, I can't say I noticed it. It did, however, suddenly become somewhat more cartoonish than previously (like a character running off a cliff and only falling when he noticed it...) It wasn't very fitting, in my opinion.
Sound: The sound of Nadia is good but not notable. I watched the subbed version and the voices were fine. They suited their characters and the performances were good, as far as I can tell. Nothing much to say on this. In any case, the soundtrack was composed by Shirou Sagisu, so you know its good. The action-comedy parts and the epic struggle for the fate of the world are both handled nicely, but Sagisu's tracks for the bittersweet scenes really shine. I can safely say the score greatly enhances the emotions of the last episodes, especially the ending.
Character: Nadia's characters are, in a word, great. The leads and supporting cast are all very well developed, but even the minor bit parts aren't left as two-dimensional ciphers. The relationships between them are very carefully crafted and actually change believably over time and with new revelations. I personally rooted for Nadia and Jean's romance.
Especially noteworthy is Gargoyle, who is, in truth, a world-class villain and one of the best I've seen in anime. He appears in only about a third of the episodes, but comes off as a true menace who you really learn to hate by the end.
The worst offense of the filler arc is probably the messing with characterization. Nadia herself is by far the worst victim of this. While she has a canonically difficult personality, the the filler arc upgrades this to "annoying bitch". Every flash of likability is negated by another act of irritating stupidity. Especially retarded is her falling in love with some random African kid - a huge slap in the face of the love story that forms the core of the whole series. Thankfully, this and most everything else that happens in the island and Africa arcs is pretty much ignored later on.
Enjoyment: While one can certainly like Nadia solely for its artistic competence, it's also damn good fun. It's been a while since I watched a series as engrossing as Nadia. It's humorous moments are amusing and its sad moments are ridiculously touching. I've rarely come as close to crying while watching an anime as during the ending of Nadia. The characters are likable and easy to get into. The series doesn't take itself seriously all the time, but when it does, so do you.
Overall: Nadia, the Secret of Blue Water isn't nearly as well-regarded as it should be. I saw a bit of it as a child on television, and expected to at least nostalgically like it when I rewatched it. Instead, the series forced its way into my Top 10 list. It's an undervalued classic that most people have not heard of and possibly never will because of its age. Do yourself a favor and watch it. And you wouldn't be doing yourself a disservice if you only watched episodes 1-22, 30, 31, 35-39.
