Cats are descended from desert animals, and as such, they have evolved to conserve water.
Cats have thick fur that helps to keep them warm. When they get wet, their fur can become heavy and matted, which can make them uncomfortable.
Cats have sensitive skin that can be easily irritated by water. This is especially true for cats with allergies.
Cats have very sensitive hearing, and the sound of running water can be very startling to them. This can make them anxious and fearful of water.
Cats have poor depth perception, which can make it difficult for them to judge the distance of water. This can make them more likely to fall in and get scared.
If a cat has had a negative experience with water in the past, such as being dropped in a bathtub or getting caught in the rain, they are more likely to develop a fear of water.
Some breeds of cats are more likely to be afraid of water than others. For example, Siamese cats are known for their aversion to water.