Marnie Blue and her school friends are spending the weekend at CORAL, an activity centre in Mermaid Lagoon. There will be lots of fun things to do, like playing with the water catapult and singing round the bubble fire. Not to mention midnight snacks! But Marnie is secretly scared: she's heard all the ghostly tales about the shipwreck that lies nearby. Can she brave the weekend away long enough to find out the secret of the spooky shipwreck?