manage to do it?"
"We have air sacs in our bodies that look like little balloons,"
said the duck. "When these sacs are filled with air, we stay
afloat; and when we want to dive under the water, we pump
the air out of those air sacs. So we can dive easily because
there is less air left in our bodies."
"So, you can stay on top of the water, and you can dive under
it, and you can swim beautifully," said Ahmad.
The duck went on: "It is because of our webbed feet that we can
swim so easily. When we move our feet forward or backward in
the water, these webs spread out and allow us to push ourselves
against the water with more force."
"Just like the flippers that grown-ups put on their feet when they
go swimming in the summer so they can swim faster and easier!"
exclaimed Ahmad.
"That's it, Ahmad," the duck agreed. "If your human feet were
like that you would not be able to walk comfortably. Because we
are water birds, however, the shape of our feet lets us swim
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