Why does Helen compare her life to a ship at sea in dense fog?

Writers often use particular techniques to not only engage the reader but help them fully understand the intended meaning of the work. Helen Keller is no exception.
In her autobiography, The Story of My Life, Helen uses a simile and several metaphors to compare her life before and after beginning her education. She writes:

“Have you ever been at sea in a dense fog, when it seemed as if a tangible white darkness shut you in, and the great ship, tense and anxious, groped her way toward the shore with plummet and sounding-line, and you waited with beating heart for something to happen? I was like that ship before my education began, only I was without compass or sounding-line, and had no way of knowing how near the harbour was. ‘Light! give me light!’ was the wordless cry of my soul, and the light of love shone on me in that very hour.”

In essence, this quote suggests that without education, Helen was rudderless and her life had no clear direction. Her blindness was a hindrance, and she implies that even if she did have a path to follow, she wouldn’t have any way to get there safely.
Helen uses the fog, or "a tangible white darkness," to represent her blindness and the way this kept her away from everything. She implies that her lack of education continued to keep her in the dark, locked away from the world.
She then uses a simile to compare a lost ship and the stumbling journey of her life before education. She also mentions "compass or sounding-line," which are metaphors for the knowledge, skills, and tools that education gave her to guide her to a fulfilling life.
From this quote, we can see how valuable education was for Helen. Her language helps us to better understand her perspective, offering insight into the life of someone without sight.
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