688 Attack Sub is a submarine simulation game programmed by John W. Ratcliff and Paul Grace that was published by Electronic Arts in 1989 for PC MS-DOS and in 1990 for the Amiga. In 1991 it was also ported to the Genesis and was released by Sega alongside M-1 Abrams Battle Tank in the extremely short-lived "Simulator Series". In Japan a version for the NEC PC-98 was released in 1991 by Cross Media Soft.
As the commander of a nuclear submarine, the player either sides with the American or the Soviet Navy. He commands either the eponymous USS Los Angeles (SSN-688) or the USS Dallas (SSN-700), both Los Angeles-class submarines, or an Alfa-class Soviet submarine. A total of ten individual missions have to be completed, ranging from the small, such as shaking off an opposing sub, to full scale participation in World War III.
The PC version also offered the possibility to play two players in distributed roles against each other via modem(or null modem cable). Furthermore, the game was accompanied by a comprehensive manual, which informed the player in addition to the direct game instructions and the copy protection also tactics and technique of submarine warfare. Included were also a glossary for technical terms and data sheets of all vehicles and weapons contained in the game. Last but not least, the manual also contained some personal comments by the developer John W. Ratcliff.