Answer: The central idea of lines 47-56 is how the man survived after struggling from being thrown to the sea.
Explanation: The text conveys the general idea that due to the frightening storm that hit the boat, the man was thrown to the sea and nearly perished. Nevertheless, he was pulled by the same rope and brought to the surface, safe, and sound. Although the passage implies that he lived for many more years and it described his future, the main idea of it is to tell the reader how he managed to handle this difficult moment.