Researchers undertake seismic studies to find out if there is bedrock or water.
Sea level is projected to rise by 3.5 to 34.6 inches between 1990 and 2100 leading to inundation.
The report projects significant dip in GDP growth of Africa, southeast Asia, India, Brazil & Mexico.
A jump in global average temperatures of 1.5 degree Celsius to two degrees Celsius will see the collapse of Antarctic ice shelves.
Vast glaciers in West Antarctica seem to be locked in an irreversible thaw linked to global warming that may push up sea levels for centuries, scientists said on Monday.
"Such intense and destructive storms are likely to become more frequent in the future as global warming intensifies", said Greenpeace.
Each degree Celsius rise in global temperatures is likely to raise world's sea levels by more than 2 metres within the next 2,000 years, a new study has warned.