Cuttlefish

The smallest thing can change the path of history.
The year is 1976, and the British Empire still spans the globe. Coal drives the world, and the smog of it hangs thick over the canals of London.
Clara Calland is on the run. Hunted, along with her scientist mother, by Menshevik spies and Imperial soldiers, they flee Ireland for London. They must escape airships, treachery and capture. Under flooded London's canals they join the rebels who live in the dank tunnels there.
Tim Barnabas is one of the under people, born to the secret town of drowned London, place of anti-imperialist republicans and Irish rebels, part of the Liberty - the people who would see a return to older values and free elections. Seeing no further than his next meal, Tim has hired on as a submariner on the "Cuttlefish," a coal fired submarine that runs smuggled cargoes beneath the steamship patrols, to the fortress America and beyond.
When the ravening Imperial soldiery comes, Clara and her mother are forced to flee aboard the "Cuttlefish." Hunted like beasts, the submarine and her crew must undertake a desperate voyage across the world, from the Faeroes to the Caribbean and finally across the Pacific to find safety. But only Clara and Tim Barnabas can steer them past treachery and disaster, to freedom in Westralia. Carried with them--a lost scientific secret that threatens the very heart of Imperial power. "From the Hardcover edition."