The Bandai Pocket Sonar: The Game Boy That Could Find Fish

Of all the strange things the Game Boy was asked to do, this might be the strangest. In 1998, the toy giant Bandai released an accessory that turned Nintendo's little grey handheld into a genuine, working fish finder. It was not a joke, and it was not a game pretending to be science. It was real sonar, in your pocket.

Fish Boy - Bandai's Pocket Sonar Fish Finder

The Pocket Sonar is exactly the kind of beautiful oddity that makes collecting the DMG-01 so rewarding, and it remains one of the most surprising items in the whole collection.

What Is the Game Boy Pocket Sonar?

Released only in Japan in 1998, the Bandai Pocket Sonar, or Gyogin Tanchiki, was a fishing tool built around a Game Boy cartridge. It was recognised by Guinness World Records as the first sonar-enabled peripheral for a games console. Where most cartridges held a game, this one held the brains of a real depth sounder, the sort of device serious anglers bolt to a boat.

How It Worked

The setup was wonderfully low-tech and clever at the same time. The base unit plugged into the Game Boy's cartridge port, and a long wire lead ran from it to a small floating transmitter. You sealed the Game Boy inside the included waterproof case, tossed the transmitter out onto the water, and the sonar pulses did the rest, mapping what lay beneath the surface and drawing it on that famous green screen. The transmitter sent its ultrasound at a 20 degree angle and could detect down to around seven metres.

Surprisingly Capable

This was no gimmick. The Pocket Sonar let you change how the fish icons looked, adjust the scroll speed, zoom in, turn the view of the lake bed on and off, and focus on a specific slice of the water column. For a 1998 accessory running on a monochrome handheld, that is a genuinely thoughtful feature set, and by all accounts it actually worked out on the water.

More Than a Gadget

Bandai did not stop at the hardware. The cartridge also included a built-in fishing encyclopedia, entirely in Japanese, and even a small fishing game to play when the real fish were not biting. It was, in effect, three things at once: a serious tool, a reference book and a toy, all squeezed into a single grey cartridge.

Why the Game Boy Pocket Sonar Is a Collector's Gem

Because it never left Japan and appealed to a very narrow audience, the Pocket Sonar is uncommon today, especially complete with its waterproof case and transmitter. For a collector it is a perfect conversation piece: proof that Nintendo's platform was seen not just as a toy but as a pocket computer that clever companies could bend to almost any purpose. Explore more unusual corners of the hardware in the Knowledge Base.