Christmas in 2004, a 9.1 magnitude earthquake under the Indian Ocean triggered tsunami waves that killed some 230,000 people across a dozen countries.

The boy once known as “Baby 81,” who was pulled from the mud as an infant after the devastating Indian Ocean tsunami in 2004 and reunited with his parents following an emotional court battle, is now a 20-year-old dreaming of higher education.

People gathered in prayer and visited mass graves in Indonesia’s Aceh province on Thursday to mark 20 years since the massive Indian Ocean tsunami hit the region in one of modern history’s worst natural disasters.

Understanding of the Sumatran subduction zone and its hazards has increased since the 2004 Indian Ocean earthquake and tsunami.

People started gathering in prayer today and visiting mass graves in Aceh, one of the worst-hit areas by the Boxing Day Indian Ocean tsunami which killed an estimated 230,000 people across a dozen countries.

Indian Ocean tsunami commemorated its 20th anniversary. Countries such as India, Thailand, Indonesia, and Sri Lanka held memorial services, dispersing flowers into the sea and lighting candles in remembrance of the victims.