The Thing About Jellyfish by Ali Benjamin

After her best friend dies in a drowning accident, Suzy is convinced that the true cause of the tragedy must have been a rare jellyfish sting--things don't just happen for no reason. Retreating into a silent world of imagination, she crafts a plan to prove her theory--even if it means traveling the globe, alone. Suzy's achingly heartfelt journey explores life, death, the astonishing wonder of the universe...and the potential for love and hope right next door.