It's a warm summer's day, so Boy and his grandad pack up their provisions and head for the seaside. There's so much to do, from exploring rock pools to building a magnificent sandcastle. But their day takes a different turn when they go for a swim and find a baby seal caught up in a net. Its rescue leads Boy and Grandad on a thrilling underwater adventure!All the excitement of a day at the beach is captured with Sam Usher's stunning illustrations in this classic book, the fourth in a highly collectable series, following on from WILD, FREE and LOST.