How Fish Finders Work

• Fish finders work by emitting sound waves into the water. When the waves hit an object, they bounce back to the fish finder, which receives and translates the data. By calculating the amount of time it takes for a sound wave to return, as well as detecting any changes in the frequency of the sound wave, the fish finder can determine depth and sometimes density of an object. That means that fish finders can help you locate fish and get a view of the underwater terrain.
  
  

Used with GPS

• Modern fish finders often integrate GPS features. In commercial fishing it helps to know not only where the fish are located in the water, but also the exact geographic location of the boat. That way, fishermen can return to the same spot if it proved productive or if it was home to a notable feature--for example, a sunken shipwreck or rock formation.
  
  

Sensitivity

• Fish finders vary in terms of sensitivity. Basic models may only show the location of an object underwater. However, more advanced devices are often able to tell the difference between fish, logs and rocks, for example. This is due to the subtle changes that occur to sound waves when they bounce off different substances.
  
  

Display

• Fish finders usually have a digital display that shows the results of the device's sonar scan. Fish finders with GPS integration will also display your location. With higher-end units, you might get a larger screen with more detailed information. The best may display different icons, depending on whether you're above a fish, some weed, a rock or a mud bottom.
  
  

Other Uses

• Fish finders use a technology that has a wide range of applications. After all, sonar is the same technique used by World War II submarines. For example, according to the Rhode Island Sea Grant College, fish finders can be useful in determining the condition of the ocean floor--much like aerial photography is used to view land above the waterline.