This society can either be utopian, based on an ingenious re-creation of society's comforts (as in Swiss Family Robinson and, in a humorous form, Gilligan's Island) or a regression into savagery (the major theme of both Lord of the Flies and The Beach). In reality, small coral atolls or islands usually have no source of fresh water (thus precluding any long-term human survival), but at times a fresh water lens (Ghyben–Herzberg lens) can be reached with a well.[citation needed]