An AUV, or Autonomous Underwater Vehicle, is a type of unmanned submersible that operates underwater without direct human control. AUVs are equipped with sensors and cameras and are used for various applications, including:

1. **Marine Research**: Exploring underwater environments, studying marine life, and collecting data on oceanographic conditions.
2. **Surveying**: Mapping seabeds, conducting geological surveys, and inspecting underwater pipelines and infrastructure.
3. **Military Operations**: Performing reconnaissance, mine detection, and underwater surveillance.
4. **Search and Recovery**: Assisting in searching for sunken ships or aircraft and recovering lost items from the ocean floor.
5. **Environmental Monitoring**: Assessing the health of marine ecosystems and monitoring changes in habitats.

AUVs are typically pre-programmed with missions and can navigate through challenging underwater environments using a combination of GPS (when near the surface), inertial navigation, and acoustic positioning systems. They come in various shapes and sizes, depending on their intended use, and can operate at different depths and in various ocean conditions.