Phillip assumes his father and other men are in boats looking for him, but what does Phillip fail to understand in Theodore Taylor's The Cay?

In Theodore Taylor's The Cay, Phillip assumes his father has ships out looking for Phillip, but what Phillip doesn't realize is that he and Timothy could be in a section of the cays surrounded by coral reefs, which make it impossible for any vessels other than fishing boats and airplanes to come near them.

At first, Timothy encourages the thought that they could soon be rescued by a ship, like a schooner. He says that if they are near the cays, then they are on the ships' route to Jamaica. But, Timothy changes his tune the deeper they drift into the cays. When they reach land, though Timothy doesn't say so at first, he is fairly certain they are in Devil's Mouth, which is surrounded by coral reefs and not a place ships can reach. Timothy keeps his suspicion a secret until he knows for certain, allowing Phillip to still believe his "father had planes and ships out looking for [them]" (p. 54).

After exploring the island they reach, Timothy is certain they are in Devil's Mouth and shares his knowledge. He explains that Devil's Mouth is u-shaped and surrounded on either side by "sharp coral banks" that extend forty or fifty miles (p. 61). It is then that Phillip realizes "no ships will pass even close to us. Not even schooners!" (p. 61). Phillip also fails to realize that it is because Timothy had begun to understand they were drifting towards coral reefs that he decided their best chance of survival was to land on one of the cays; he was beginning to realize they were not in the ships' route after all. Yet, Timothy remains optimistic, believing that certain planes will pass overhead and that they will be able to attract a passing plane with a signal fire.