Why does Timothy decide to abandon the raft and go to the desolate island that contains no drinking water in Theodore Taylor's The Cay?

In Theodore Taylor's The Cay, one reason why Timothy feels it is better to go to the island rather than remain on the raft is because he knows that drifting towards the cays is inevitable. With all of the jagged shores of the cays, it's much safer to remain stationary on an island rather than to continue to drift in the tangle of multiple cays. One of the greatest reasons is that Timothy knows it will be far easier to establish shelter and find food on the island than it will be aboard the raft. Most importantly, Timothy has come to realize they have drifted into a spot called Devil's Mouth, surrounded by coral banks, which means not many ships sail that way, decreasing their chances of rescue. Therefore, Timothy knows the surest way for them to be rescued is by building a large signal fire on the island that planes passing overhead can see.

Once on land, Timothy rejoices in the soft feel of the sand and says they'll be able to make themselves a very comfortable camp. He also says encouragingly, "Many feesh 'ere. Langostaita, too, I b'known'. We ros' dem" (p. 58). He is also optimistic that they will be able to easily replenish their water supply by catching it during the first rainfall. After Timothy explores the island, while eating some of their provisions from the raft, Timothy confesses they may be in Devil's Mouth, surrounded by coral banks. But, he remains optimistic that building a large signal fire is the best way to be noticed by planes passing overhead.