The sea turned green amid an algal bloom on a beach in Thailand.

Nueng Nattakarn and his friends witnessed the disgusting verdant waters during their holiday in Chonburi on June 4.

The phenomenon was expected to last for around a week before the sea turns back to normal, locals said.

Plankton, or microalgae, are tiny organisms that live in the water, both in the ocean and in freshwater bodies. They are unable to swim against currents, so they drift with the water.

Algae blooms happen when there is excessive nitrogen and phosphorus in the water, and phytoplankton drift in the sea. This phenomenon could last up to a few weeks.

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.