X-COM: Terror from the Deep Windows, DOS, PS1 game

The war continues. The alien terror spreads into a whole new dimension. Seeking to take advantage of a weakened Earth, X-Com's deep-space foes unexpectedly change strategy and launch a powerful second front against planet Earth. In the dark depths of the vast oceans, long-sleeping forces are awakened by reanimation signals sent out across the galactic silence by their interstellar brothers and sisters. Slowly but surely, an army of hibernating alien sea creatures awakens. Your combat now extends to the strange, new worlds of the deep, where the superior alien technologies threaten the very survival of this planet - your planet - Earth.