Underwater vehicles are machines designed to operate beneath the surface of the water. They can be manned, like submarines, or unmanned, such as remotely operated vehicles (ROVs). These vehicles are used for various purposes, including scientific research, underwater exploration, and military operations. Many underwater vehicles are equipped with cameras and sensors to gather data about marine life and underwater environments. Some are also used for tasks like inspecting underwater pipelines or recovering objects from the ocean floor. Notable examples include the Alvin submersible and the Deepsea Challenger vehicle.