A depth sounder is a device used to measure the depth of water beneath a vessel. It operates by sending sound waves from the surface down to the seabed. When these sound waves hit the bottom, they bounce back to the device, allowing it to calculate the depth based on the time it takes for the echo to return. Depth sounders are commonly used in various marine applications, including fishing, navigation, and underwater exploration. They help boaters avoid shallow areas and obstacles, ensuring safe travel on water. Many modern depth sounders are integrated with GPS systems for enhanced functionality.