Sasthamcotta Lake, Freshwater lake in Kollam District, Kerala, India

Sasthamcotta Lake covers 375 hectares in Kollam District, its water held along the southern side by a 1.5 km earthen embankment that separates it from paddy fields bordering the alluvial plains of the Kallada River. The other shores rise into steep hills forming narrow valleys, and smaller water bodies and waterlogged areas lie to the south and southwest.

The lake received Ramsar designation in 2002, acknowledging its international importance as a wetland habitat. This recognition reflected growing efforts to protect its ecosystems and wildlife populations.

The lake takes its name from the ancient Sastha temple on its bank, where resident troops of monkeys are part of the temple surroundings. A ferry service across the water links West Kallada and Sasthamkotta, carrying people between the two shores.

The lake is accessible for visitors who want to explore by foot or boat around its perimeter. Early morning visits offer the best experience when wildlife is most active and temperatures are cooler.

Tiny aquatic larvae called cavaborus live in the lake and naturally purify the water by consuming harmful bacteria. This biological filtration system works constantly without needing external intervention.