A duck is swimming in a lake. A dog is sitting in her tail. If the duck dives, what happens to the dog ?

Question

A duck arrives near a lake. He sees a sign were it is written "No swimming allowed.", but the duck jumps into the water.
Why?

Answer 1

Ducks dont have tail.

Answer 2

How can a dog sit on the duck's tail while the duck is swimming..

Answer 3

The duck is simply a duck (not mentioned as female)
here her refers to whom is a question (may be the dog itself)
therefore nothing will happen to the dog if the duck dives.