First, mammoth waves washed over their villages, leaving not a single hut standing.
Then the survivors' ordeal began: days of thirst, hunger and kilometers of walking until -- just at the point of rescue -- a hungry pack of crocodiles tried to snap them up.
The refugees lived to tell the tale, thanks to some Indian seamen who shot at the menacing crocodiles as the fleeing refugees made their way to a rescue ship.
"As we were returning, two or three crocodiles started coming toward us," Sister Charity, a 32-year-old nun, said on Thursday.
"The navy officers had to fire their revolvers to ward off the crocodiles to protect us," she said.
Sister Charity, who was rescued from Hut Bay island, was among survivors who told harrowing stories as they emerged from the isolated Andaman and Nicobar islands.
Crocodiles are common across Southeast Asia and the South Pacific and are among the many dangers survivors are facing after Sunday's disaster.
After a tsunami in Papua New Guinea several years ago, crocodiles feasted on corpses scattered along the beaches.
In this remote spot in India, rescuers followed the stench to find rotting corpses in jungles on the 30 or so of the territory's 500 islands that are inhabited, officials said.
Survivors brought to Port Blair, the territory's capital, said they had not eaten for two days and also had to fend off the crocodiles that were swept ashore by the huge waves.
Mohammad Yusef, a 60-year-old fisherman from Tea Top village on Car Nicobar island, said his village was wiped out.
"There's not a single hut which is standing," he said.
Yusef said he and his extended family of 20 walked a dozen kilometers to reach a devastated but functioning airfield on the island where thousands of people were being evacuated by India's air force.
His family was brought to a Catholic church in Port Blair.
Yusef said there were about 15 villages around Car Nicobar's shore and all were destroyed.
"Everything is gone. Most of the people have gone up to the hills and are afraid to come down," he said.
Despite their travails, some people vowed to return home and start again.
"We are broken, but this is not the end of life," said George Aberdeen, a 25-year-old coconut farmer whose village on Car Nicobar was washed away by Sunday's tsunami.
"We will rebuild our lives. It will be difficult -- but the whole family will do it together," he said.
Just how many villages and families remain was unclear.
The International Red Cross said 30,000 people might be missing on the island chains, which are more than 1,120km southeast of India's mainland and have a population of 350,000.
The islands' administrator, Lieutenant Governor Ram Kapse, said about 400 bodies had been cremated or buried and 3,000 were missing.
Authorities prevented journalists and representatives of international aid groups such as Oxfam, Doctors Without Borders and CARE from visiting the islands to assess the damage and death toll.
At a makeshift refugee center at the Nirmala Convent School, papier-mache stars still hung from the Christmas Mass as hundreds of people sat under blue plastic tarps while women in white saris served bowls of rice and lentils.
Langley Matenga, George Aberdeen's brother-in-law, told of how he and his family of 10 fled the waves that engulfed their village, Mallaca, where some 500 Hindu, Muslim and Christian families lived.