Any odours emanating from the cat's body are usually due to the skin and coat. Check the general condition of the fur - it could simply be that your cat has gotten particularly dirty - but if the coat appears to be in good condition, carefully tease your way through the fur to look for wounds
General skin infections will also be whiffy, so check your cat's body for signs of damage or irritation. In such cases, the coat can often feel greasy, especially if your cat isn't grooming properly.
When you get close enough, a cat's bottom is bound to smell, but you're looking for particularly foul odours. This could be caused by diarrhoea in cats, and you'll notice stools around the bottom in this case because your feline friend hasn't been able to adequately clean the area - especially if the problem persists.
It's also a good idea to look around the ears. These are often smelly areas caused by ear mite infestations, bacterial ear infections, or yeast infections.
You don't always have to smell a cat to notice an issue in this area, because a cat may scratch at their ears far more than usual. If your cat has smelly ears, take him or her to the vet right away so that the problem can be treated.
As you will have read, there are numerous reasons why a cat may smell, and introducing a kitty to water will not necessarily solve the problem. Sure, there are methods for bathing a cat that will remove any dirt they may have picked up while also leaving them smelling better.