The waters of a popular Vietnamese beach turned green as algal blooms erupted along the coastline.

Footage shows the murky green sea on the shoreline of Ho Chi Minh City, or Saigon, as tourists and locals swam on the afternoon of October 25.

Some concerned holidaymakers chose to leave the water after noticing its unusual colour, which resembled a matcha tea drink.

Pham Khac To, Director of the Centre for Culture, Information, Sports and Tourism of Vung Tau Ward (HCMC), said the phenomenon occurs yearly and does not affect the health of beachgoers.

He added: 'This is caused by moss or algae growing rapidly over a short period, which changes the colour of the water.

'This phenomenon only lasts a few days, at most about a week, before disappearing naturally. The seawater will then return to its usual clarity.'

The coast guard remained on duty to ensure the safety of tourists on the beach.

Algae blooms happen when there is excessive nitrogen and phosphorus in the water.

People who swim in beaches with algae could experience skin rashes, eye irritation, vomiting, diarrhoea, fever, or cold-like symptoms, and muscle and joint pain.