X-COM: Terror from the Deep is a turn-based strategy game released in 1994 as a sequel to X-COM: UFO Defense. Players control a global defense organization tasked with combating an alien threat emerging from the oceans. The game features base management, research, and tactical combat against various underwater alien species. In Terror from the Deep, players must gather resources, develop technology, and deploy soldiers in missions to thwart alien invasions. The game introduces new elements like underwater environments and different alien factions, enhancing the strategic depth and challenge compared to its predecessor.