Captain Barnacles woke up, his voice echoing deeply in the quiet room. He tried coughing, drinking water, but nothing seemed to change his new deep voice.

Shellington and Professor Inkling woke up to find their voices had deepened too. They exchanged surprised looks, their voices rumbling in the quiet room.

Kwazii and Peso woke up and walked into the dining room, their appearances altered to resemble children. They sounded and looked like kids, causing them to flare up in frustration.

An adult man and woman walked in, interrupting Kwazii and Peso. They gently guided the two to school, ignoring their protests and colorful language.

Tweak and Dashi found themselves unchanged. Their voices remained the same, leaving them confused and worried about their friends.

The team gathered, discussing their strange transformations and the mysterious soundwave that seemed to be the cause. They decided to investigate, hoping to reverse the effects.

The Octonauts set off, determined to solve the mystery of the soundwave. Their journey took them deeper into the ocean, navigating through treacherous currents and strange creatures.

They faced challenges, their new appearances proving to be more of a hindrance than they had imagined. But they persevered, their determination unwavering.

The Octonauts reached a mysterious underwater cave. It was filled with strange, glowing plants and creatures, the source of the soundwave hidden somewhere within.

They explored the cave, their eyes wide with wonder and caution. They were close, they could feel it. The solution to their problem was within reach.

In the heart of the cave, they found a mysterious device. It was large and round, glowing with a pulsating light. It was the source of the soundwave.

They approached the device carefully, unsure of what it would do. They needed to deactivate it, to reverse the effects of the soundwave. But how?

Each of the Octonauts tried to deactivate the device, using their unique skills. Yet, nothing seemed to work. The device continued to pulsate, its light growing brighter.

Just when they thought all was lost, Kwazii and Peso stepped forward. Despite their childlike appearances, they had a plan. And it was their last hope.

Kwazii and Peso started to sing. Their voices, though childish, echoed through the chamber. The device seemed to respond, its pulsating light syncing with their song.

As the song reached its climax, the device's light dimmed. And then, with a final note, it powered down. The chamber fell silent, the glow fading away.

Slowly, the Octonauts started to change. Their appearances reverted back to their original forms, their voices returning to normal. They had done it. They had reversed the effects of the soundwave.

Their joy was contagious, their relief palpable. They had faced a challenge unlike any other and had come out victorious. They were the Octonauts, and they were ready for any adventure.

With their mission complete, the Octonauts returned to the Octopod. They waved goodbye to the cave, the source of their adventure, ready to return to their normal lives.

As they navigated through the ocean, they couldn't help but reminisce about their adventure. It was a tale they would tell for years to come, a story of bravery, determination, and friendship.

Back at the Octopod, life returned to normal. The Octonauts went back to their daily routines, their adventure becoming a cherished memory. They were ready for whatever came next.

The ocean was vast, filled with mysteries waiting to be explored. And the Octonauts, brave and ready, would face them head-on. For they were not just a team, they were a family.