Municipal water liability cases often require distinguishing between several related but distinct theories: liability for a dangerous physical condition of the property itself, such as a hidden underwater hazard; liability for a failure to warn about a known danger that the agency did not create but knew about; and liability connected to the design or construction of water infrastructure, such as a diversion structure, spillway, or flood control feature, that itself created the hazard. Each theory may require different evidence and can carry different defenses, particularly where a public agency argues that a specific design decision is protected by design immunity under California's public entity tort statutes.