For five cousins, a summer holiday by the sea was supposed to be about sunshine and sandcastles. They never expected to find a secret world beneath the waves.When a rogue wave washes away their sandy creation, it reveals something far more amazing: an entrance to a magical grotto. Led by the quick-thinking Elvira, she and her cousins-sensible Lyra, daring Finn, and the inseparable younger duo, Maya and Tom-are plunged into an underwater realm of shimmering wonders. They meet friendly merfolk and make an unforgettable friend in Olen, a wise and gentle sea turtle so giant he seems to hold all the ocean's secrets.But their adventure takes a heartfelt turn when they find a tiny, glowing squid, a Lumina, lost and alone in the shadows. Its light is fading, and it can't find its way home through a dark, forgotten tunnel. With the help of the wise Olen, the cousins learn they are the only ones who can guide the little creature to safety.Their quest will test their courage and creativity as they work together, using the magic of the grotto itself to light the way. It's an enchanting adventure about teamwork, empathy, and discovering that the greatest magic of all is the courage found in friendship. Will their plan be enough to reunite the little Lumina with its family before its light fades forever?