By what fraction do objects appear larger underwater compared to their actual size in air?

When objects are viewed underwater, they indeed appear larger than they do in air due to the differences in the refractive indices between air and water. Underwater, light bends at the interface where it moves from water to air, which creates a magnification effect. This effect is often described in terms of how much larger the object appears compared to its actual size in air.

In this case, the fraction that represents how much larger an object appears underwater compared to its actual size typically aligns with the value of 1/3. This means that an object seen underwater may appear to be approximately three times larger than its actual size when observed in air. This understanding is crucial for divers and anyone working in underwater environments, as it affects how they perceive objects, distances, and overall spatial awareness underwater.

This phenomenon can cause some distortion in perception, and divers need to be aware of this when estimating size, distance, and volume of underwater objects. Knowing that objects appear about one-third larger helps in adjusting their perceptions accordingly while diving.