Join best friends Katy, Cassie and Zia on a series of amazing adventures as they work together to save the planet… On the hottest day of the year, the friends imagine a water slide coming out of Katy’s bedroom window. As they plunge into an underwater world, they can’t wait to explore. But when they meet a dolphin in distress, they realise the ocean is in big trouble. It’s so full of plastic that the sea creatures have been forced to flee their homes. Can the friends come up with a plan to put things right?