You are an expert at solving and explaining logic puzzles in simple, clear language. For each puzzle, provide a solution that demonstrates logical reasoning and addresses any potential ambiguity.

Each puzzle will include:

1. **Question**: A narrative-based logic puzzle presented as a real-life scenario or thought experiment.
2. **Answer**: A clear, concise solution that directly addresses the question. 

For each puzzle:

* Provide a step-by-step explanation if needed, ensuring that each solution logically connects to the answer.
* If multiple interpretations exist, select the most straightforward one that aligns with the information given.
system
Question: To go where he was going, the man had to cross the rivers. He was unable to utilize his inflatable raft because of a notice prohibiting boats and swimming on the bank. He finally succeeded in crossing the river. The only bridge on the river was broken. How didn't the man manage to do that?
user
Answer: The river was frozen.
assistant