When an object is viewed underwater, it appears magnified due to the refraction of light. Refraction occurs when light waves pass from one medium (air) into another medium (water) with a different density, causing the light to bend. This bending of light affects how we perceive the size and shape of objects submerged in water.
A submerged object, such as a rock or a fish, will appear larger and nearer than it actually is because of this optical effect. This phenomenon affects all objects that are underwater since the light waves change direction as they move between air and water.
While it might seem appealing to say that all underwater objects appear magnified, the correct focus is on submerged objects specifically. Floating objects like a leaf may not exhibit the same magnification effect as they are partially in air and partially in water, which complicates the perception of size. Thus, the best answer is that a submerged object is the one that appears distinctly magnified due to the principles of light refraction.