What is the reason objects underwater appear larger and closer?

Objects underwater appear larger and closer primarily due to refraction, which is the bending of light rays as they pass from one medium to another, in this case, from air into water. When light travels from air (a less dense medium) into water (a denser medium), it slows down and bends towards the normal line, which is an imaginary line perpendicular to the surface at the point of entry.

This bending of light alters how we perceive the size and distance of underwater objects. As a result, when a diver looks at an object under the water, the light rays that reach their eyes have been refracted, making the object appear magnified and seemingly closer than it actually is. This phenomenon is particularly important for divers to understand, as it can affect their distance judgment and the overall perception while navigating underwater.

Refraction is a fundamental concept in optics and is crucial for activities like scuba diving, as it influences visibility and the way underwater environments are perceived. The other concepts listed do not contribute to the perceived size and closeness in this context; for instance, reflection pertains to light bouncing off surfaces, absorption relates to the loss of intensity of light traveling through a medium, and dilation is not relevant in this optical context.