The Zaratan is a gigantic sea turtle described in folklore and literature, whose shell looks like a sloped, rocky mound several hundred feet in diameter. Sailers mistakenly see its shell as a small tropical island, so they drop anchor and land. When night falls the monster sinks beneath the waves, dragging down the ship and drowning them all. The Zaratan is alternatively described as a giant whale or octopus, or a great fish that strives night and day to bring his tail to his mouth but cannot because he is so large.
When a Zaratan gets hungry, it opens its mouth wide and releases a sweet smell. Fish are attracted to the odor and swim in, when its mouth is full it snaps its jaws shut, similar to an alligator snapping turtle.
A Zaratan depicted as a whale appears in the tale of Sinbad the sailor.
Zaratan is catalogued in The Book of Imaginary Beings.
A Zaratan could also be original place of the lost city of Atlantis when suddenly the beast dove under and destroyed the settlement.
The Zaratan resembles the World Turtle, a giant turtle or tortoise with the world on its back.
An explanation for this massive creature is sighting of prehistoric turtle, like 4 meter long and 5 meter wide Archelon from late Cretaceous or even larger Stupendemys from Cenozoic eras, we can rule out Stupendemys as it is a freshwater turtle. But still, they didn't even came close to the size of small island that Zaratan is described. With the advent of modern technology it easy to tell if some gigantic creature appear in the surface or not, that's why sightings of Nessie is doubted. But remember, less than 0.05 percent of our ocean is already mapped, there is still possibility down there, if they even evolved to deep seas.