India, Sept. 29 -- Optical illusions are a great way to test your brain's comprehension powers and the sharpness of your eyesight. These types of illusions usually feature a scene that seems normal at first sight, but which has, amidst other objects, a special feature that is hidden and not easy to spot.

One such intriguing optical illusion has a picture of water-laden pebbles and shrubs, possibly on the edge of a pond. Among these inanimate objects lies a bright green frog that is hard to spot despite its distinctive features.

This is a tough brain teaser, as there are several elements in the picture making it difficult to spot the frog. The presence of water, with many stones partially submerged, makes it all the more difficult to see...