Dear teachers,

Would you please explain to me the underlined expression?

A child on the tour said he would like to see a beaver, since he had heard there were many in the park. The guide said he would do his best. First he led us along a road, and then we turned off onto a path. To our right was a marshy pond.
Suddenly the child who had spoken before shouted, "Look! I see a beaver!" Of course the beaver was startled. It slapped its tail and disappeared into pond.

Why isn't there an article between "into" and "pond"?

Many thanks,