Codename: ICEMAN was one of Sierra On-Line's lesser known graphical adventure games. The game has a Cold War era plot involving a global oil shortage, an oil discovery in Tunisia and a kidnapped ambassador. You play the role of a naval officer who must participate in the rescue mission of the ambassador.
While this game was a step forward in terms of the technical sophistication of Sierra's graphical adventures, it just didn't make for as good of a game as their more popular series like King's Quest, Space Quest, etc. A significant part of the game involves a submarine simulator. However, being primarily a graphical adventure game, this simulator isn't detailed enough to be that interesting. In addition, It's fairly easy to get into unwinnable situations and not realize it until you are pretty far away from the decision point that caused it. Nevertheless, if you are a fan of Sierra's graphical adventures, this one is at least worth checking out.
Codename: ICEMAN was released for the Amiga, Atari ST and DOS based computers in November 1989. You can find originals on eBay for the original platforms with wildly varying prices. The good news is that this game is also compatible with ScummVM and can be played on a wide variety of modern platforms via that emulator.
Screen shots above are from the Atari ST version of the game.