The world is overpopulated by about three billion people, resulting in an all-encompassing famine. One company has happened upon a technological solution to purify the world's water and make infertile lands bloom, which would be great for everybody. Unfortunately, terrorists also happen to be anti-technology and believe that thinning down the population by more "traditional" means is the best way to solve the world's problems.

Enter Kate Wilson, an assistant engineer who saw none of the events of Hydrophobia coming. During an anniversary party aboard the city-ship "Queen of the World," the aforementioned terrorists take over, taking her associates out of commission. Kate goes out to investigate and is quickly caught up in a struggle for survival and a quest to thwart the terrorist scheme in any way she can.

At its heart, Hydrophobia is just as much an engine showcase as it is a game. Dark Energy Digital has crafted two proprietary engines that render the title unique. The first is their InfiniteWorlds game creation system, which allows for high-resolution graphics and multiple game assets that fall within the size limits for Xbox Live Arcade titles. The result is actually not so much an "arcade" title at all but a full-fledged, story-laden saga usually only seen in disc media.

While the game is indeed visually stunning, Hydrophobia's greatest asset is arguably how one plays it. This is where Dark Energy Digital's HydroEngine comes into play. With it in place, water behaves naturally, flowing where it wishes based on how the environment is set up at the time. It can help or it can hurt, and players must adapt on the fly if a well-laid watery trap goes wrong. Water can aid in drowning enemies, electrocuting them, or submerging entire rooms underwater for submerged combat — and all of these can just as easily be turned against you. This adds an extra layer of unpredictability atop the variations that can happen simply due to individual play style.

The result is a shooter bereft of memorization, where thought and full knowledge of every environment is just as important as marksmanship or reflexes. Do you try to inch toward your opponents to take them out the old-fashioned way, try to destroy them via remote control with environmental and water hazards, or take the fight underwater? It's all up to you, and once again, thanks to the variable nature of the water, replayability is assured. My personal hands-on time with Hydrophobia also reassured an easy learning curve, and once the controls and nature of the game are learned, an uncontrollable urge to experiment takes over. Hydrophobia is set to hit Xbox Live Arcade on Sept. 29, so it won't be long before other players will attain the urge as well.