David sat in the dark hold of the boat named Believe in God, fighting thirst and nausea. He and forty-three other Haitians were crossing the ocean toward the Bahamas where they planned to board another boat and head for Florida. But their dream of entering the United States illegally quickly receded in the face of misery and fear.

Between 6,000 to 12,000 Haitians enter the United States illegally every year, according to Michael Finkel, a journalist who traveled with David aboard the Believe in God. The U.S. Coast Guard estimates that thousands of other immigrants perish each year in the turbulent seas near the Bahamas. Like most immigrants, Haitians leave their country—the poorest in the Western hemisphere—in order to find work.

Illegal immigrants travel to the United States by sea, land, or air. Sea travel is especially perilous...