Island of Whispers by Frances Hardinge

On the island of Merlank, the Dead must not be allowed to linger. The very sight of their ghosts can kill you.

When young Milo is thrust into the role of Ferryman following his father’s sudden death, he is the one who must carry away the Dead. Pursued by a vengeful lord and two malignant magicians, Milo must navigate strange and perilous seas where untold threats whisper in the mist. Does he have the courage and imagination to complete his urgent mission?