Available only in Japan, the Gameboy pocket Sonar was a device designed for fishermen who also happened to play Gameboy. The device consisted of a gameboy cartridge to which was attached a reasonable length lead, at the end of which was a cylindrical object, that just so happened to be the sonar itself. The user would dangle the sonar in the water where they expected to find fish. The sonar would emit a sonar frequency, and the gameboy screen would show what was found, including locations of fish. They could then cast their line and hope for a catch. Besides being a ridiculous substitute for a real fishfinder, the Gameboy pocket sonar also made for a great conversation piece.