WordWorld - Castles in the Sea/Sandbox Surprise

We will be showing a different episode of WordWorld here each week! In Castles in the Sea, Duck and Shark discover a perfect home for Shark while playing on the beach, a sand castle! The only problem is it disappears every night while Shark is sleeping. The WordFriends try to hunt down the castle thief, and they learn about tides and waves from a singing Crab. In Sandbox Surprise, Duck and Dog become curious about compound words when they discover the word sandbox is made of two words. How many words can they pull apart in WordWorld before chaos breaks loose?