Villagers in Nam O Village, Lien Chieu District are now usually seen busy collecting the seaweed that grows on the rock surfaces by the sea between October and January.
During this time, local fishermen cannot go fishing out in the sea due to high waves, and they turn to collecting seaweed.
This is hard and dangerous work when people have to climb slippery cliffs.
This is also the roughest time at sea and people can only collect the plant during the morning time when the tide falls.
Sometimes they get hit by high and strong waves.
Nguyen Thi Lua, 43, said that she usually sets out to search for the plant at midnight.
"We wear tight clothing, gloves and bring some simple tools including some bags and a blade," she said. "We usually work from 1-10 am and collect between 5-10 kilos of seaweed."
Pham Van Thang, 54, said that they have been collecting seaweed for generations.
"This work usually brings us good income during this time," he said. "This year I earn between VND 20-30 million a month from collecting seaweed."
Seaweed can be made into some good soup with fish or meat. It can also be dried and preserved for later use. A kilo of dried seaweed is priced between VND600,000-700,000 (USD33).