Seas cover 70% of our planet, and are full of life. But we are not taking very good care of the sea. Sometimes we treat the sea like a great big dustbin. Rubbish, plastic, sewage and dangerous chemicals all end up in the sea, and this can harm the animals and plants that live there. Or we use big boats and big nets to catch fish - and catch more than we need, or hurt animals with our nets.

Now the animals have had enough - it's time to fight back! But how can they do it?

"Stop! Listen!" whistled the Pink Dolphin, raising his pink beak high. "We must plan our attack with the skills and intelligence we alone possess. We can see more and hear more than any human. We have the power to locate their every move."

"You mean 'echolocation'?" asked a dolphin calf.

"That's right, " replied the Pink Dolphin. "We can all learn the high-pitched call dolphins use to find fish and detect danger. If our call bounces back we know exactly what's at sea and where it is. That's how we can fight back!"

For weeks the Pink Dolphin trained the sea creatures to make the high-pitched call. Soon they could identify each other from far away, and could track the fishing boats as soon as they left the port.

"First we must show them we are not afraid of their nets and knives!" whistled the Pink Dolphin. "We must stop them from catching our fish!"

"But that's impossible!" cried the sardines. "Their boats are so big and their nets are so strong!"

"Nothing is impossible for us!" said the Swordfish. "Here's our plan…"

Read next page