Doesn't this movie have a deeper message?
**SPOILERS** obviously
Maybe I am thinking too much into a creature movie, but ... The daughter is right about the age hormones start kicking in and dads stereotypically want their daughters to stay children forever. Could the creatures represent the hormones or inevitable path of puberty for a teenage girl. The hormonal changes basically can take over an adolescents mind, creating a "new" person. The father doesn't like the changes and fights to get his "old" daughter back, or at least understand what she is going through.
There are tons of subtle clues throughout the movie. Just the fact that the creatures come from a mound of dirt - earth being a representation of fertility and woman. When the daughter is first attacked, the father breaks a glass and cuts himself and the camera does a close-up of the blood in the water. The blood could be representing just his daughters blood as she is attacked, or it could be representing the exact moment of her first period and the beginning of her change.
And in the end, the creatures win and the change takes place. The last thing you see is the creatures coming for the little boy - a foreshadowing of the boys own eventual changes...
Maybe I just need sleep...