From the Beagle Bros Winter 1980-81 catalog: Find the invisible subs in your Apple color graphics scope before your oxygen and fuel run out! Use your deep-sea scanner switch and watch for the blips that give clues to each sub's whereabouts. A scan-tracer shows you where you have looked, and if you are unable to locate all subs, the computer reveals their locations in comparison to where you have searched. A final score printout lets you compare your success with others.