The hidden dragon / Melissa Marr.

Enhanced descriptions from Syndetics:

A sea-faring girl and her friends take on pirates and grown-ups, and bond with dragons, as they work to make the world a better place, in this spellbinding fantasy by New York Times bestselling author Melissa Marr.

Otter (short for Ottilie) is a girl who is most comfortable on her family's ship, the Tempest , where she and her fathers collect the dragon hides that protect the queen's guards. But all is not well in the kingdom, and it's not clear if the queen is to blame. The streets are full of homeless kids, and now one of them, a street-smart boy called London, has stowed away on the Tempest . He befriends Otter, and soon they realize that the fate of the kingdom needs to be in the hands of the kids. For in every tight spot-during pirate attacks and navigating the magical land of the Netherwhere, where they get ship-wrecked-it is the quick-witted kids who save the day. As they work to fight injustice and protect the defenseless, they earn the respect of the realm's most magical creatures-dragons and gargoyles-who all bond together as a force for good. Melissa Marr spins another fabulous fantasy, centred on family and friends, and introduces readers to the most splendid magical creatures.