Holly is a nine-year-old superhero known as 'Underwater Ballerina'. She always wears a pink long-sleeved full-body rubber wetsuit covered in sparkles, a pair of pink swimming goggles, a pair of pink rubber gloves, a pink swimming cap, a pair of pink underwater ballet shoes and a pink tutu. She is part of a superhero club with her two sisters Olivia and Wendy, who are aged 5 and 11 respectively. Olivia is known as 'Sparkle Swimmer', and she always wears a blue sparkly long-sleeved full-body rubber wetsuit, a pair of cyan swimming goggles, a pair of teal rubber gloves, a blue swimming cap and a pair of light blue flippers. Wendy is known as 'Flamboyant Diver', and she always wears a lavender long-sleeved full-body rubber wetsuit, a pair of fuchsia swimming goggles, a pair of light pink rubber gloves, a mauve swimming cap with a tiara on top, a light purple superhero cape and a pair of pink flippers. The three sisters live together in a huge house with lots of swimming pools and they love each other dearly. They always keep their superhero outfits on all the time, even when they go to bed!