Descendants (2008)

In a post apocalyptic world where man has decimated the Earth, breathing the air turns people into zombies.  The populace only ventures out in gas masks.  But a small number of children born with marks on their necks are immune to the effects of the air.  They can go outside without being encumbered by masks.  They are also safe from the infected as zombies do not attack them.

Camille, one of those born with the neck marks, promises her mother she'll travel to the coast to find safety where the great octopus is... wait, what?  Did I hear that right? Yup, she said octopus.

Camille is entrusted with the care of two younger children just like her.  The three travel towards the coast, meet other kids, and try to keep from being killed by the military who are killing kids outside who can breathe the air.

Again, another zombie story with potential which doesn't pan out.  Numerous flashbacks to Camile and her mother, men in hazmat suits, and carnage provide the back story.  Much of the footage with her mother is extremely annoying due to the mother's screeching.

The cover is extremely misleading as there is nothing even remotely like this in the movie.