Thousands of people fled beaches on Indonesia's resort island of Bali in a tsunami drill yesterday, kicking off remembrances across Asia two years after the tragedy in which 230,000 people died and millions were left homeless.
Elsewhere across the disaster zone, survivors and mourners marked the anniversary by visiting mass graves, lighting candles along beaches, chiming temple bells and observing two minutes of silence.
Some volunteers planted mangroves, saying they were key to protecting coastal communities.
The 9.0-magnitude earthquake that ripped apart the ocean floor off Indonesia's Sumatra island on Boxing Day 2004 spawned giant waves that fanned out across the Indian Ocean at aircraft speeds, causing death and destruction in a dozen countries.
Walls of water two storeys high swept entire villages out to sea in Indonesia and Sri Lanka, submerged luxury resorts and fishing communities in Thailand and destroyed thousands of homes in India.
The drill - which involved real-time warnings sent from the capital to radios along the beach - was as much about raising awareness as testing technology deployed in the country hardest hit two years ago.
Nearly 167,000 of those killed were from Aceh province - nowhere near Bali - where tens of thousands of people still live in temporary homes.
Sirens wailed as masses, many of them school children, briskly walked inland from the shore, accompanied by Indonesia's minister of research and technology and a handful of foreign tourists.
But not everyone was moving. "I'm not going anywhere, I still have to make some money this morning," said Wati, a woman who was selling baked corn on the cob on the beach.
In Thailand, ceremonies will be held along the Andaman coast with Buddhist prayers to remember more than 8,200 killed. Balloons will be launched and candles lit along beaches once again filled with sun-seeking tourists. Authorities will also open a cemetery for hundreds of unidentified tsunami victims.
"We hope this will be part of the healing process for those who lost loved ones," said Chamroen Tankasem, a government official in southern Thailand, a tropical paradise that was turned into a graveyard in minutes.
"It will also help us remember what happened, what we have learned since and what more needs to be done for the people affected."
In Sri Lanka, the resurgence of a civil war has added to the misery of survivors and slowed efforts to rebuild - sparking criticism yesterday from outgoing United Nations secretary general Kofi Annan, who urged Tamil Tiger rebels and the military to lay down their arms.
"No one could have prevented the tsunami's wave of destruction," he wrote in a statement.
"But together, we can stem the tide of conflict, which threatens once again to engulf the people of Sri Lanka."
While many in the island nation were preoccupied with war yesterday, Hindu and Buddhist temples rang bells to mark the time the first wave hit followed by a two-minute silence to remember the 35,000 killed.
In India, where another 18,000 are believe to have died, interfaith ceremonies were held and in Malaysia, where 69 people were killed, volunteers replanted mangroves.