Wet? Why Not?

Riddle: A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it?

Answer: The river was frozen.

Source: https://www.riddles.com/9814

A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it? — Wet? Why not? by Sarah Anwar Siddiqui v1.

Riddle: A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it? Answer: The river was frozen. — by Sarah Anwar Siddiqui v2.