Stinging, salty waves crashed over the deck as frantic figures climbed on board. It was midnight in November, and we were 30 miles off the coast of Libya, where our small ship was quickly filling with scores of terrified, freezing refugees whom we had rescued from the chilly waters. I stepped over an elderly paraplegic man sprawled on the deck so I could wrap blankets around a teenage Egyptian boy battling hypothermia. His eyes rolled back in his head as he tried to stay awake.

“Doctor, my name is Rafiq,” he told me in broken English. “I am alone. I am 15 years old. If I die, please tell my family.”

I peeled his clothes from his clammy body and wrapped my arms around him to try to keep him warm. I felt his heartbeat flutter and wondered if he would make it until morning. Beside him, the paraplegic man searched in vain for his small knapsack, which he had lost during the rescue. Nearby, a Sudanese mother cradled a wailing, emaciated 40-day-old baby covered in lumpy skin lesions.

These refugees, and others like them, risked everything to make this treacherous journey because the lives they left behind posed an even greater danger than the sea. The Syrian war has displaced millions who are desperately seeking an existence free from barrel bombs and chemical weapons. Others travel thousands of miles over land and water to escape poverty and authoritarian governments. Most of these migrants flow through Libya in the hope of making it to Italy by boat across the Mediterranean Sea — since 2015, nearly half a million have reached the Italian coast. From there, many continue their travels into Europe.