From C64CG website, "You're flying a Fuel Injected Sardine Hyper-drive (or F.I.S.H.) through space when all of a sudden you discover that there's loads of random crap just hanging around in space and it's right in the flight path of your fish, so you have to dodge through the gaps in order to survive!

Instructions: Joystick in port 2, move up and down to guide your fish and dodge through the gaps in the... stuff."