This riddle says: A dog is on one side of a river and its owner is on the other. The dog crosses without using a bridge or boat and without getting wet. How?
The answer is: the river is frozen.
If the surface of the river is covered with solid ice, the dog can simply walk across it. No bridge or boat is needed, and the dog does not have to enter the water.
The trick is that most people automatically picture the river as flowing liquid water. The riddle never actually says that the river is unfrozen.
Once you remove that assumption, the solution becomes simple. Cold weather turns the river into a solid path, allowing the dog to cross safely without getting wet.
