Travel to the ocean
The people who have survived the initial climate disaster spend most of their life trying to travel to the ocean so that they will have potable drinking water. However, the water in the ocean is contaminated and salt water, making the water actively harmful to drink (drinking salt water dehydrates people).
Ransom's profession
Although Ransom is a doctor and an incredibly intelligent man, the people around him reject his professional advice. This is unexpected: people usually actively seek the advice of real professionals like Ransom. They don't ignore them unless they are incompetent (and Ransom is certainly not incompetent).
Doctor
Similarly, many of the characters in the novel continue to call Ransom "doctor" despite not fully trusting him and his advice. People who do not trust another person's opinion or professional credentials would not usually continue call them by their earned title.
Ransom's pleasure in the drought
Part of the way through the novel, Ransom lets readers know that he takes a certain pleasure in the drought. This is unexpected and shocking: the drought has made Ransom's life (and the lives of those around him) much harder and significantly worse. Most would not take any pleasure in the misery that the drought has caused.
Ransom's smile
Ransom's smile is described as "dreamy" and "ironic." Ransom's smile is neither dreamy nor ironic. Instead, it is straightforward and almost completely devoid of irony.
