Photos of the beast were posted on Reddit, under the title "By God, it's a monster!" by a user who said he worked for a deep-sea surveying company. His crew found the creature hooked onto the bottom of a remotely operated vehicle, and estimated that the behemoth -- which measures 2 1/2 feet long -- was creeping along at a depth of about 8,500 feet.
Nearly 800 commenters responded to the initial query, with reactions that ranged from outright disgust to culinary craving.
"Damn, Nature. You scary!" wrote one.
"Nasty things, but I heard the meat's not too bad," responded another.
Online investigations also helped identify the critter, which is a Bathynomus giganteus, or giant isopod. The crustaceans are related to shrimp and crabs, and are thought to dwell in the deep seas of the Atlantic and Pacific oceans.
Their name suggests otherwise, but most giant isopods are less than a foot long -- making the recent deep-sea discovery a supersized version. That could be because of a condition called gigantism, which is suspected to be common among crustaceans inhabiting particularly cold water regions.
"In crustaceans, bathymetric gigantism may also in part reflect decreases in temperature leading to longer lifespans and thus larger sizes in indeterminate growers," writes C.R. McClain, a deep-sea biological systems expert who blogs at Deep Sea News.
In the 1990s, an expedition off the coast of Australia reinforced the speculation. Researchers found that the deeper the water, the larger the lurking isopods.
Giant isopods might make tasty prey, but they're also hungry predators: The scavengers feast on carcasses of dead whales and fish. They have been known to attack sea-dwellers that are still alive and swimming.
That zealous appetite is probably one reason they've survived so long: Fossil records date these cockroaches of the sea back more than 160 million years, before the Earth's continents were even formed.
And while the timing of the critter's Web debut sparked skepticism that it was nothing more than a supersized April Fools' gag, McClain, for one, is convinced.
""I've seen the pictures, and they are real, and they really do get that big," he said.
With a gross-out factor on par with last year's tongue-eating parasite, it's hard to believe that this giant isopod might not even be the ultimate example of the species. Notes Deep Sea News blogger Kevin Zelnio, "the maximum reported size of Bathynomus giganteus is likely to be an artifact of our sampling."