Economic shocks stemming from rising sea-levels pose a long-term risk to the sovereign credit-ratings of dozens of countries which have large areas at risk of submersion, including Vietnam, Egypt, Suriname and the Bahamas, Moody's said. Climate science suggests that sea-levels will continue to rise for decades, contributing to increasingly frequent natural-disasters such as storm surges, floods and cyclones, the credit-rating-agency said in a report.