Colombo is shaped by its relationship to the Indian Ocean and an intricate network of inland waterways.
- **The Laccadive Sea (Indian Ocean)**: Forms the western border of the city, defining its climate, trade, and culture. - **Kelani River**: A major river forming the northern boundary of the city, emptying into the ocean and serving as a crucial water source. - **Beira Lake**: A large lake in the heart of the city (Colombo 2), historically used by the Portuguese and Dutch to transport goods within the city. It features the Seema Malaka temple on its waters. - **Diyawanna Oya**: A lake system surrounding the Sri Lankan Parliament building in Sri Jayawardenepura Kotte, adjacent to Colombo.