The Term “fish Finder” Is Often Used To Refer To Two Different Types Of Fishing Instruments: Sonar And Radar. Sonar Is A Technique That Uses Sound Waves To Locate Objects Underwater. It Was Developed In The 1960s And Has Been Used By The Navy Since World War Ii For Submarine Detection. Radar Operates By Transmitting Radio Waves Into Water And Then Detecting Them As They Bounce Back Off Objects Such As Fish, Other Vessels, Or The Sea Floor Below. Modern Radars Can Be Used For Imaging And Mapping Of Undersea Terrain. Sonar: Sonar Sends Out Pulses Of Sound Waves, Which Bounce-Off Any Object In Their Path And Return Information About It To A Receiver On The Boat Or Ship. The Object's Size And Shape Can Be Determined By Measuring The Time It