Bermuda Triangle
As the Golden Age of video games neared its end, many developers put players into familiar environments, like outer space or a maze. But Data Age gave players Bermuda Triangle, one of the very few 2600 titles to take players beneath the sea for a fast-paced side-scroller that would make Jacques Cousteau proclaim "Zees is ze boolsheet! I totally shot zat shark! Merde!"
Gameplay: Mysterious artifacts abound on the sea floor. Your mission is to collect as many as you can, then safely deliver them to your research vessel on the surface. However, these tropical waters are swarming with giant sharks and squids, and if you come into contact with them, you lose artifacts and become temporarily paralyzed. Because you're in the Bermuda Triangle, there are also UFOs, semi-intelligent floating mines, a laser gun that appears out of nowhere to randomly blast you, and a mysterious ship that chases your research vessel across the surface. If you come into contact with any of them, you explode. Fortunately, your sub has a laser cannon, and you've presumably got lightning-quick reflexes, so put them together and dive! Dive! Dive!
Could be mistaken for: Defender, 50 different episodes of In Search Of… with Leonard Nimoy, SeaQuest DSV