The island is the most important part of the TV show aspect of the plot. Truman is deliberately raised to believe that the island upon which the show is set is the only place where he can feel safe, where he experiences good emotions and has a good life. When the cracks in the facade of the island start to show, Truman tries to leave, tries to reject the reality created for him by the people around him, and is consistently stopped by people who believe that they have his best interests at heart.

When he makes his sea journey—which terrifies him—the man who owns the dome in which he is held would literally rather cause his death than let him leave. This represents the attitude a lot of religious leaders, especially evangelical pastors/ministers, hold toward apostates/people leaving the church. Leaving spirituality/the religious bubble is considered WORSE THAN DEATH.

When Truman finally speaks to his “god”—Christoff, the dome owner—Christoff tells him, perhaps truthfully, that life in the dome is far safer, far calmer, far more sure and known than life outside the dome. And Truman, staring into the blackness beyond the dome, makes the deliberate decision to say goodbye—to go out into a world he cannot predict or ever truly be sure of—so that he can truly start to live.