Why did Miss Sullivan repeatedly spell "w-a-t-e-r" into Helen's hands while pouring water over them?

So that helen would know where to find water when she was thirsty and so  she could connect the word with what it was.

Explanation:

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.