From the back of the box:
X-Com Terror from the Deep
2040 AD. Alien craft are spotted breaking the surface of the world's oceans. Liners are sunk and ports attacked. X-Com (the Extraterrestrial Combat Unit) are tasked to investigate, the sea-based terror and YOU, as Commander, are in charge. All-encompassing strategy, heart-stopping suspense, and terrifying face-to-face combat. Come on in! The water's deadly!