Domestic cats and even most wild cats avoid being submerged in water at all costs. The top layer of a cat’s fur is relatively waterproof, but the soft hair underneath quickly becomes waterlogged if exposed to submersion in water or even heavy rain. This causes their body temperature to plummet, which is extremely uncomfortable. The wild ancestors of domestic cats specialised in hunting small land animals, and never needed to enter water.
Unlike humans that need water to keep clean, cats have a specialised tongue to help rid their fur of debris. Hook-shaped papillae make the tongue rough. These tiny barbs act like a comb and remove dirt from the fur as well as teasing out any knots.
There are exceptions, and wild cats from hot climates tend to enter water voluntarily. Some pet cats enjoy being in water, especially if they live in a hot climate. Both tigers and jaguars are frequent swimmers, and some cats specialise in catching and eating fish.
Image from flickr.com/photos/macabrephotographer