In 1970, a powerful cyclone killed nearly half a million people along the coastline of Bangladesh.

Some 138,000 people perished in yet another cyclone that mauled its coastline two decades later.

Cyclones, famine and floods are so common in the South Asian nation that singer-songwriter Joan Baez once lamented: "When the sun sinks in the West, die a million people of Bangladesh."

Not this time around. Bangladeshis are thanking their lucky stars and wondering how they came out of Sunday's quake-tsunami calamity relatively unscathed. While tens of thousands have died in neighbouring India, Sri Lanka and Thailand more than 120,000 people have died in 11 Asian and African nations only two Bangladeshi children drowned on Sunday when their boat capsized in the high waves.

While that's two too many, it still left locals with their mouths agape.

"I still can't just believe my luck. We are safe, when nations close to us have been mauled so badly," said Mansur Ahmad, a Dhaka businessman who was vacationing on Sunday among 15,000 tourists in St. Martin, an island off Bangladesh's southern coast.

He said high tides in the Bay of Bengal were the only signs something was amiss. When panicked phone calls from the mainland started coming in, they headed for higher ground.

"And then we realised that we were in danger and we left the island in panic," said Ahmad, who was with his family, including a 4-year-old daughter.

Geologists attributed Bangladesh's good luck to a natural process of sedimentation, making the sea bed shallow along the coast.

Billions of tonnes of sediment, which the country's numerous rivers carry into the sea, have created a natural barrier against tsunami, said Mir Fazlul Karim, a geologist at the state-run Geological Survey of Bangladesh.

The barrier helped slow the sea surges before they hit the coast, Karim said.

He said the barrier has helped keep the sea floor shallow the coastal water in Bangladesh is up to 20 metres deep and "absorb the impact of the tsunami".

Bangladesh's coast is more prepared, naturally, than its neighbouring countries to protect lives from sea surges.

The 170-km coast also has more than 2,000 multistoreyed buildings used to shelter people fleeing disasters, said Golam Rabbani, head of Bangladesh's Red Crescent Society the Islamic equivalent of the Red Cross in Chittagong, a seaside city to the southeast.

"We are well prepared to face cyclones and tidal surges," Rabbani said.

"But we feel so relieved that nothing serious happened this time."

"Allah has saved us," he said.

The 140 million people of Bangladesh are predominantly Muslim.