The working principle of a fish finder is mainly based on sonar technology. It contains a sonar sensor inside. When the fish finder operates, it emits a series of sound waves at specific frequencies. These sound waves travel through the water and interact with fish. By emitting sound waves and receiving the reflected waves, the fish finder can obtain the location of the target and underwater information. Different types of fish finders are available to suit different usage scenarios.

A fish finder usually consists of a receiver and a transmitter. The transmitter floats on the water surface and is responsible for sending sonar signals underwater. The receiver is responsible for receiving the reflected sonar signals and generating an image of the fish based on the feedback.

In addition to detecting the location of fish, a fish finder can also detect water depth, water temperature, and the contour of the seabed. Moreover, apart from sonar technology, some fish finders can also provide an underwater visual perspective. These types of fish finders are typically equipped with a camera, allowing for better observation of the underwater environment and fish biting the hook.