The time period of the novel is important, as it is set during World War II. Once the Dutch were attacked by Germany in 1940, their territories were in danger of attack. It is because of German attacks on the oil refineries and tankers that Phillip is stranded.
The Cay is set in the Caribbean. This area of the world is full of many little islands. Because of this, Phillip and Timothy are able to find an island to survive on after the S. S. Hato sinks.
The weather in the Caribbean is tropical. At first, it is easier for Phillip and Timothy to survive. They don't need warm clothing and find plenty to eat. The climate also brings hurricanes. A massive hurricane kills Timothy and puts Phillip in grave danger.