A thick layer of algae turned the waters of Marina Bay outside the Fullerton Bay Hotel, NTUC Centre and the Promontory @ Marina Bay a rich emerald green yesterday.
Experts said a combination of hot sun and heavy rain might have caused the widespread algae bloom.
Dr Patrick Martin, research fellow at Earth Observatory of Singapore, Nanyang Technological University, said: "The heavy rain over the past couple of weeks might have caused more nutrient run-off from land, which is fuelling the bloom."
The warm weather would have caused the algae to bloom, said Mr Chan Wei Loong, Republic Polytech-nic's Programme Chair, diploma in marine science and aquaculture.
National water agency PUB said algae growth was "naturally present" in Singapore's waterways and it moves up to the water surface at night to be ready for photosynthesis at sunrise. "This is why algae are usually more visible from the early morning to the mid-afternoon."