No. Chihuahuas shed and thus leave pet dander in your home. Dander is the cause of most pet-related allergies. Because Chihuahuas are small, however, you can manage their fur and dander more effectively than you can the hair and dander from a medium or large dog.
Because of their small size, Chihuahuas sometimes possess a Napoleon complex, with a tendency to growl and nip at those bigger than themselves. But if you put yourself in a Chihuahua's tiny paws, it's easy to imagine why they can get a bit defensive. Chihuahuas are not naturally mean, they just need to be well-trained and socialized, and have their personal space respected.
Chihuahuas often shiver because they're cold—many Chihuahuas will appreciate a sweater or dog coat if it's cool—inside or out. But anxiety or overexcitement can also cause shivering; if your Chihuahua shivers frequently, take him to the veterinarian for a checkup.
Chihuahuas may be able to swim, but probably won't want to—at least not beyond a minute or two. Big bodies of water can be scary for this tiny breed, and they chill quickly.