Tik-Tok of Oz by L. Frank Baum

The waves dashed and the lightning flashed and the thunder rolled and the ship struck a rock. Betsy Bobbin was running across the deck and the shock sent her flying through the air until she fell with a splash into the dark blue water. The same shock caught Hank, a thin little, sad-faced mule, and tumbled him also into the sea, far from the ship's side.

When Betsy came up, gasping for breath because the wet plunge had surprised her, she reached out in the dark and grabbed a bunch of hair. At first she thought it was the end of a rope, but presently she heard a dismal "Hee-haw! " and knew she was holding fast to the end of Hank's tail.