Once upon a time, in a small town by the sea, there lived two curious and brave siblings, Mateo and Amalia. Mateo was 5 years old and always had questions about everything around him. Amalia, who was 3 years old, was playful and affectionate. They loved exploring the world together and had many animal friends who joined them on their adventures. There was Nora, the clever and cunning cat, Samba, the outgoing and talkative parrot, and Pol, the calm and wise panda.

One sunny day, Mateo and Amalia were sitting by the beach, watching the waves crashing against the shore. They saw colorful fish swimming in the clear blue water and wondered, 'Why can fish breathe underwater?'

Just as they were pondering this question, Nora, Samba, and Pol appeared. Nora, with her sharp ears, had heard their question and had an idea. She told them about a magical underwater adventure that would help them find the answer.

Excitedly, Mateo, Amalia, Nora, Samba, and Pol followed a trail of sparkling light that led them to a hidden cave below the ocean's surface. As they entered the cave, they found themselves surrounded by shimmering crystals that illuminated the entire space.

In the center of the cave was a wise old turtle named Bobby. Bobby had a gentle voice and a kind smile. He welcomed the children and animals and asked, 'I heard you have a question about fish breathing underwater. Would you like to hear a magical story that will explain it?'

The siblings and their animal friends nodded eagerly, and Bobby began his tale. 'Long ago, when the world was still being created, all animals needed air to breathe, just like humans do. But as time went on, the Creator realized that some animals would need to live underwater. So, the Creator created a special organ called gills that allowed fish to extract oxygen from water and breathe comfortably.'

Mateo and Amalia listened intently as Bobby continued, 'Imagine gills as tiny filters in the fish's body. These filters extract oxygen from the water and remove harmful substances, allowing the fish to thrive in their underwater homes. Fish are truly remarkable creatures!'

With wide eyes, the children and animals were now full of wonder and awe. They couldn't wait to share this newfound knowledge with their friends and family.

As they bid farewell to Bobby and made their way back to the beach, Mateo and Amalia couldn't stop talking about all the amazing things they had learned. They knew that the ocean held so many secrets, and they were excited to uncover more of them in their future adventures.