The Lake Of Tears by Emily Rodda

Lief, Barda and Jasmine continue their journey to restore the magical Belt of Deltora, traveling to a mist-shrouded lake where an enchantment of sorrow grips the land; there they must uncover hidden secrets, outwit dangerous foes and deceptive magic, and free the oppressed people as they search for the next gem that will bring hope back to their world.