The Sorcerer of the High Seas

He stole a drink of milk. He ended up on a ship of sorcerer-pirates hunting for the soul of the sea itself.
Finnian "Finn" Wavecutter is a dockside orphan with a secret knack: he can coax water to flow. It's a talent that keeps him alive, until the day he's caught stealing milk from the prized cow of a ruthless merchant. His panicked escape unleashes a torrent of magic he never knew he possessed-and catches the eye of the most dangerous crew on the ocean.
"Rescued" from the city guards, Finn is thrown into a world of salt, sorcery, and brutal discipline. He is forced to become "Cadet Rook," a kidnapped student aboard the Maelstrom's Heart, a legendary ship that serves as a school for magically-gifted pirates. Their mission: to find the Tear of the Leviathan, an artifact of unimaginable power that can command the seas.
But Finn soon learns the horrifying truth. The Admiralty doesn't want to teach him to wield magic; they want to use him as a living battery for their shadowy leader. Trapped between a fanatical cult that wants to sacrifice him and the tyrannical pirates who want to drain him, Finn's only hope lies with a rebellious fellow cadet and a band of rogue free-sailors, the Crimson Corsairs.
To survive, Finn must master the very power that enslaved him, uncover the secrets of the Tear, and decide where his loyalties lie. Should he claim the power for himself, destroy it, or let the sea claim it forever? The fate of the world will rest on the choice of a milk-thief.
Perfect for fans of The Pirates of the Caribbean and Harry Potter, this thrilling debut launches an epic trilogy of magic, high-seas adventure, and the search for a place to call home.