Cleo is in a bad mood. Her shell is getting too tight for her bum, and she needs a new one. Together with her father, they set off to find the perfect shell. But Cleo gets impatient and makes a mistake that could be deadly for many sea creatures. Will help arrive in time to rescue Cleo from harm? Join Cleo in this entertaining, rhyming story as she makes an amazing discovery about hermit crabs and learns how plastic pollution affects sea creatures.