This is Liu Baichen's third ocean voyage. The 48-year-old ophthalmologist is again traveling with Chinese hospital ship No 866, nicknamed Peace Ark, on a four-month medical mission overseas.

On a previous Peace Ark mission to Djibouti in 2010, Liu cured a man from the slums who had lost his sight to cataracts. When Liu removed the bandages from the patient's eyes after the operation, the 53-year-old man jumped up from his bed and hugged him.

"For three years, he had been living in darkness, but suddenly he could see again," said Liu. "I couldn't understand his language but I could see the excitement in his face and eyes. The joy of being healthy is universal."

Liu said regaining his sight meant the patient was no longer a burden on his poverty-stricken family and he was able to start a new life.

"As a doctor, I felt so proud to see him smile," said Liu, who has been an ophthalmologist at the General Hospital of the Chinese Navy in Beijing for 23 years. "I have been working in China for a long time, and now I am able to help people in other countries."

At the sound of a steam whistle, Peace Ark, a 178-meter-long white vessel with red crosses painted on her decks and sides, sailed from the port of Zhoushan in East China's Zhejiang province on June 10. During the voyage, she will visit eight countries, including Indonesia, Pakistan and India, providing free medical services to the local population.