Twins Chirri & Chirra are pedalling on their bicycles when they find a cave:

 

“Let’s take a look, Chirri.”
“Yes let’s go, Chirra.”

 

With those opening words, the twins in their matching white dresses (only a blue pocket differentiates Chirra from Chirri’s red pocket) ride their bikes into a tunnel, headlights illuminating the path ahead. They arrive under the sea. “Oh,” the rosy-cheeked twins say as they pedal in the water, surrounded by fish, coral and algae.