My Take: Bad adaptation of a terrific Jules Verne novel.
The video cover forced me to buy this "adaptation" of Jules Verne's continuation of his 20,000 Leagues Under the Sea. This one didn't actually apply a Jules Verne-style fantasy adventure. Video covers are among the things that force you to buy a movie, so don't always fall for such tricks. But "Mysterious Island" isn't totally a horrible movie, but it is a bad one no doubt about it. The CG effects are lame and sloppily made. I prefer Ray Harryhausen's stop-motion monsters (who animated them on the original adaptation in the 1960's) any day. The acting lacks energy, which is an essential if you are making an adventure movie, made-for-TV or otherwise.
Anyway, your better off reading the book again.
TV movie rating: * out of 5.