#12 in the Little Tim series:
Tim becomes ill, pining for the sea. His father determines they should take a voyage, though Tim's mother is against the idea. While at sea, Tim's father gets a wireless message saying he must return urgently. He and the mother are put ashore, but the boys (Tim and Ginger) remain aboard as workers. Then the captain and others fall ill. Ginger is made ship's cook (which is not good at), and the second mate takes over the steering -- in the wrong direction. But he refuses to listen to reason until it's almost too late. An extra big wave sweeps them clear of the rocks. Later in front of the captain, the mate blames Tim for the bad steering, but all is well in the end.