Molly was jerked out of her thoughts by a sudden scream. She glanced around to see Coral being dragged away from her by a strong whirling current.

“Come back!” she yelled without thinking, striking out after her friend.

But seconds later, she regretted it. For now, she was being pulled along by the mighty torrent of water too – and however hard Molly battled against it, she was powerless to swim in any other direction…