Fifty years ago, the ocean was becoming quiet. Whales were disappearing. Hunters killed too many of them.
In some places, only a few whales were left. Out of one hundred whales, only five remained. Scientists were worried. They thought the ocean would become silent forever.
Then, countries made a new rule. In 1986, most hunting of whales stopped. The whales had time to grow in number again.
Slowly, the whales came back. Today, in many oceans, you can hear humpback whales singing again. Their songs travel far under the water.
The story of the whales shows something important. When people decide to fix a big problem, they can really do it.