Ibrahim Musa, a 42-year-old civil servant in the hard-hit Aceh province of Indonesia, said it feels like yesterday that his family was taken by the sea.
"Even after four years, I cannot forget how I lost hold of my wife and baby," he said. "I have tried in vain to look for them for three years. Now I have no choice but to accept their departure as destiny."
Musa gathered with thousands of others along the Aceh coast, where a massive earthquake triggered the tsunami that killed 230,000 people - more than half of them in Indonesia.
Siti Hasnaini, 40, who still lives with her two sons and husband in a temporary shelter, prayed "for my daughter who was washed away with my house."
Homes for Hasnaini and nearly 900 other families are scheduled to be completed by February, a month before the Indonesian government winds up its reconstruction mandate, said government spokesman Juanda Djamal.
Total spending has reached $5.48 billion, 70 percent paid out of foreign donations, and more than 124,000 houses have been built, he said.
On Thai beaches, where thousands of locals and tourists died, family members and friends gathered for services, including one in the sand under palm trees held before hundreds of spectators.
Paulette and Bauke Van den Wyngaard, a Dutch couple who return to Patong beach every year to visit the spot where they survived the deadly surge, were among them.
"We were lucky to survive. Others were not as lucky," said Paulette, who was pulled from the raging water by a hotel worker.
In Sri Lanka, the government declared two minutes of silence for the thousands of people killed there as well as other victims of natural disasters.
The "Queen of the Sea," a coastal train toppled by the tsunami, was repaired and made its first trip in four years Friday, riding the same route where more than 1,000 of its passengers were killed in 2004.
In India, where thousands also perished, interfaith prayers and a moment of silence were held.
Hundreds of thousands of homes, schools, hospitals and businesses have been rebuilt across the region in the largest relief operation ever seen.
AP reporter Mike Casey in Bangkok contributed to this report.