Sully the grey seal pup has just been born and already he's in trouble. On a cold, wet and windy beach, he must learn all he needs to know in just four short weeks before heading out to sea alone on the journey of a lifetime. From being abandoned, to getting stranded on a rock in a storm, Sully's infanthood is full of surprises. Will he ever make it off the beach to become a wonder of the sea, able to dive deeper than 300 metres?