Whale Mail. Bureau of Magic Abuse

Picture this: you've somehow come into the possession of a dragon (long story--you can read the previous book if you really want to know, but it's kinda embarrassing, so you don't need to). And you need to return that dragon to the place it came from. You've tried putting it on a truck--but it destroyed the truck. You've tried putting it on the train--but it destroyed the carriage. Now you've put the dragon in a warehouse while you figure out what to do, but-- You guessed it: the dragon destroys the warehouse. Tell me, why wouldn't you trick some rich merchant into lending you the only thing you haven't yet tried: a boat. Trouble is, the merchant's price is that you return an old artefact to the whale kingdom along the way.
Whales are not nice. They're very big. They're cranky. And, here is a secret: they hate dragons. They especially hate dragons.