Another theme might be the unknown and the fear of the unseen. The bad water could be a carrier of something that is not immediately visible, like a supernatural force or a deadly micro - organism. This creates a sense of dread as the characters try to figure out what is wrong with the water and how to stop it from harming them. Also, the theme of isolation could be present. If the bad water affects a particular area, those in that area may be cut off from the outside world, adding to the horror as they struggle alone against the threat of the bad water.
A theme of corruption could be in 'bad water a horror story'. The water, which is usually a symbol of life and purity, is corrupted. This could represent a deeper moral or spiritual corruption in the world of the story. For instance, if a community has been engaging in unethical practices, the bad water could be a form of punishment or a manifestation of the evil they have sown. It also ties into the theme of helplessness, as the characters may feel powerless against the corrupt and dangerous water.
One possible theme could be the fear of the unknown in medical science. New treatments or diseases that are not fully understood can create a sense of horror.
Possibly, the story could explore the journey of water, like how it travels from rivers to oceans and its impact on the environment along the way. Another theme could be the role of water in different cultures and their beliefs related to it.
I'm not sure which specific 'bad water a horror story' you are referring to. There could be many horror stories related to bad water. It might involve water being contaminated with something evil, like a curse or a toxic substance that causes strange and terrifying things to happen to those who come into contact with it.
One possible theme could be adventure. Just like the journey 'there and back again', it might involve exciting experiences related to water, like exploring uncharted waterways.
The theme of isolation might be present. In open water, one can feel extremely alone and cut off from the rest of the world, and this could be a big part of the story.
One possible theme could be redemption. The bad son might realize his wrongdoings and strive to make amends.
One possible theme could be good vs. evil. Since it has 'big bad' in the title, there might be a clear distinction between a 'bad' force or character and those who oppose it.
One possible theme could be survival. If the story involves people struggling to get clean water in a drought - stricken area, survival is a major theme.
Possible themes in 'Black Water' based on a true story could include mystery. If the cause of the black water is not immediately known, it can create a sense of mystery. Also, community. The people in the area affected by the black water might come together to deal with the situation, highlighting the importance of community. And there could be a theme of change. Maybe the story shows how the area has changed because of the black water, either for better or for worse.
One possible theme could be the fear of the unknown. Since the knock is something mysterious, it represents the unknown danger lurking.