What is the main imagery of "Blue Water Djinn" and how does it relate to the theme?

The short story "Blue Water Djinn," by Tea Obreht, tells of a beach hotel and its residents, particularly a young boy named Jack and a man known only as the Frenchman, who disappears one night leaving nothing but his rumpled clothing on the beach. The story is based on the observations of the young boy, Jack, and the stories of Mr. Hafez, the manager of the hotel while Jack’s mother is away. Jack watches the scenery around him and observes the people who stay at his mother’s hotel. Mr. Hafez tells him the story of the Blue Water Djinn, a kind of demonic spirit who lures creatures to their deaths and eats them, using their skulls as cups.
Through the use of the description of the Blue Water Djinn, the image of the wrecked ship, and Jack’s observation of the Frenchman's art and the poor sea turtle, the author attempts to connect powerful imagery with the main theme of the story. Ms. Obreht uses this imagery to illustrate the theme: that the loss of innocence comes with knowledge, especially if that knowledge is sad and terrible. There is also the idea that people will do whatever they can to protect children, but eventually, children will realize what is happening and attempt to have different experiences, as Jack does in the story.
For example, Mr. Hafez describes the Blue Water Djinn in such a way as to imprint upon Jack the danger which awaits him if he runs off or attempts to swim on his own. Living near the sea is magical but also dangerous. On the shore, there is comforting imagery: beautiful colors, straw hats, tans, the warmth and weight of the sand, people milling about. Out at sea, however, there are dangers lurking past the safety of the shoreline. Mr. Hafez warns Jack about the dangers of visiting the site of the shipwreck, where the Djinn live, surrounded by the skulls of their victims, their mouths red with the flesh of men, their teeth sharp and their fingers long and spindly.
Jack sees the ship as a terrifying place, a place which is too far for him to ever go, at the “edge of the world.” The ship is rusty, green-tinged, and dark, lying on its side like an enormous dead fish. It frightens him to think of the ship and the Djinn, which represent the loss of innocence which would occur if Jack were to stop believing the stories and attempt to venture out beyond the warning signs. It represents a place like adulthood, so close, yet frightening and far at the same time.
In addition to the images of the shipwreck and the Djinn, Jack sees for himself how dangerous the sea is when people disappear or are injured. Even the poor, sad, tired sea turtle which washes up on the shore—trapped by a net and the victim of a broken, gaping shell—serves as a warning against the dangers of the sea. Jack has also seen a shark almost take the head off a tourist, who, bloodied and maimed, eventually lost an eye because of his foolishness.
Similarly, Frenchman's art depicts the creatures of the sea that they both observe. It angers Jack, however, because the Frenchman gets the colors of the Angelfish wrong. The Angelfish only shows its true colors when it’s in the water. This image shows that something is hidden, waiting to be discovered. It connects with the loss of innocence that Jack must experience when he reaches adolescence; he is frustrated by the truth being hidden from him and needs to discover that truth for himself.
Finally, after the death of the Frenchman, Jack gives in and rebels. Once he reaches the ship, he believes he will discover the terrible truth of the Djinn, but instead he discovers a lone sea turtle, trapped by the tide. It keeps attempting to get out, over and over again, but it cannot reach freedom. Like Jack, the sea turtle is innocent, lured into a trap by the lies that it believed. Now it has realized its mistake and must make its own way out, as Jack must also do. Previously, he had been tricked into not misbehaving by the vivid images and stories of the Djinn, but now, he’s discovered how naive he truly was.