Parasitic Alien Intruder from the movie The Faculty
Parasitic alien intruder in the movie The Faculty escaped to Earth because its home planet started to dry up.
It relishes water and it is most comfortable in it, but to conquer Earth and enjoy the benefits first it has to bring humans to their knees.
Which is, as we know, not the easiest of tasks. To accomplish that this parasitic alien has to blow its cover.
Apparently the alien queen is a vessel for its highy mobile and detachable offspring which infect humans using ears to get inside them. Then they reproduce in moist environment, which results in making the people very, very thirsty.
The possessed people recognize each other and pass the alien parasites on to the non-possessed ones.
Among parasitic types of aliens they have the most impressive regenerative powers. They are able to re-attach the host's head if it accidentally falls off. It seems that these little creatures have a knack for adjusting humans'personalities and emotions, too.
The progeny and the mother alien are connected telepathically so if it dies all the rest die, too. How can you kill this parasitic alien? A strong diuretic will do the job. Piece of cake. And everybody can carry on with their lives like nothing happened.