After Resident Evil redefined the survival horror genre on Sony's Playstation in 1996, Sega decided that they needed to get in on this hot new craze and set to work developing their own survival horror game. Complete withith tank controls, fixed camera angles on pre-rendered backgrounds, high octane FMVs of elevators, and horrible voice acting, 1998 saw Sega's efforts come to fruition in the form of DEEP FEAR. Instead of taking place in a mansion riddled with zombies and other horrors, DEEP FEAR takes place deep under the sea, in a military installation constructed upon the seafloor called The Big Table. It's actually a pretty cool setting, although it tends to get pretty visually same-y.
Things start going awry on The Big Table in short order. For some reason, many staff members and animals situated aboard The Big Table begin to mutate into monsters, who can then spread this mutation to others by attacking them. It's up to former Navy Seal John Mayor, no relation, to protect the remaining staff members against the burgeoning threat. Meanwhile, resident scientist Dr. Gena Weisburg researches why people are mutating in the first place, and why John seems to be immune, despite sustaining injuries from mutant attacks himself.
Where does April Fools Day come into play? Well, DEEP FEAR takes place on April 1st. Whenever John Mayor or indeed anyone aboard The Big Table try to warn anyone or ask for outside help in regards to the mutating monsters, they're laughed off because it's April Fools Day, don't you know! What, you want military reinforcements to come to The Big Table because people are mutating into monsters and killing everyone? What a jokester! Knock off your April Fools Day shenanigans and get back to work, John Mayor! Even after John Mayor rescues his friend Mookie from a mutant attack, Mookie struggles in vain to tell another disbelieving survivor about the mutation, and John stands there and says nothing.
April Fools Day being the canonical reason why a single man has to deal with an undersea zombie outbreak isn't even as goofy as this game's plot gets. DEEP FEAR never saw a release in the United States, but did see an English release in Europe. It's worth checking out just to see how silly it gets.