Fish Can't See Water
They can see the surface from below, but not the water itself, due to a 97-degree refracted view of the world above.
Fish can see the water's surface from below due to the difference in refractive index between water and air, but they do not normally see the water itself. This is because water and air are largely transparent and not normally visible.
When light is reflected and refracted where water meets air, a fish can see the water's surface. This allows them to perceive the world above the surface, although it is compressed into a circular window about 97 degrees across due to refraction.
Outside this window, the surface acts as a mirror due to total internal reflection, reflecting the underwater world back to the fish. This means that someone standing above the surface outside this window wouldn’t be directly visible.
The visibility underwater is often poorer than in air because suspended particles scatter light. Additionally, longer wavelengths of light, such as red light, are absorbed first in water, leaving mainly blue light to penetrate to greater depths.
Fish do not normally see the water around them, but instead see objects in the water and the boundaries where water meets something else. This is similar to how humans see the world, where we perceive boundaries between different media or particles suspended within them, rather than the media itself.
## Why it matters The way fish see the world is different from how humans do, and understanding this can provide insights into the unique challenges and opportunities that fish face in their environment. By recognizing how fish perceive their surroundings, we can better appreciate the complexities of underwater life and the importance of preserving aquatic ecosystems.
