It's without any decent dialog, but the story makes it fun to watch. Quite a big budget, and it's evident. All those sets. Quite impressive. I wish there was a better cinematographer to fully exploit them.
None of the performances are really good (excluding the guy who was paid to protect the soon-to-be-destroyed village out hero trades with), though I enjoyed watching the guy flying the balloon. Check his excited curiosity when meeting the mutated hero (he can breath under water). The villains are nothing above cartoonish. Maybe it was so that the movie was suitable for kids (post-apocalypse isn't exactly a light subject).
The concept of soil being the most-valued item on the water-covered earth (as a result of global warming) is interesting.