Well, it might be about the struggle against nature. Since there's 'black water rising', it could depict how the characters deal with this natural phenomenon that is encroaching on their lives. They may have to find ways to escape, adapt or overcome it.
It might be about the power of nature. The 'dark water rising' in the novel can represent nature's force that is beyond human control. It shows how humans are at the mercy of natural disasters and how they respond to such overwhelming power, whether with fear, courage or a combination of both.
I'm not entirely sure without reading the novel specifically, but usually in such a story, there could be a protagonist who is likely to be in the center of the action against the rising black water. Maybe a strong - willed individual who tries to lead others to safety.
The main theme could be mystery. It might revolve around the secrets hidden within the setting where the black water lilies are present.
The main theme of 'Red Rising' is about social class struggle. It shows a world where the society is highly stratified, and the protagonist fights against this unfair system.
I'm not sure specifically as I haven't read the novel in detail. But usually in such a story, there could be a protagonist who is a local resident trying to protect their family from the rising water.
The main theme could be mystery. Since there's'something in the water', it might imply a hidden element or danger lurking there, which often creates a sense of mystery in a story.
It could be about the exploration of a particular place or community. In 'The Water is Wide Novel', perhaps it focuses on the unique aspects of the area near the water and how the people there live, their traditions and relationships, all of which can be considered as part of the main theme.
The main theme could be mystery, as many novels with 'deep water' in the title often involve elements of the unknown or hidden things beneath the surface, both literally and metaphorically.
The main theme of 'A Memory of Water' could be the exploration of human connection and the power of nature.
Water Margins was a classical novel that mainly described the resistance of 108 righteous men, including Song Jiang, against the Liao and Xixia countries at the end of the Song Dynasty.