What visual effect occurs when objects are viewed underwater?

When objects are viewed underwater, they appear larger due to the refractive properties of water. Water has a different density than air, causing light to bend as it travels from one medium to another. This bending of light, known as refraction, makes objects under the water appear closer and larger than their actual size.

As light passes from air to water, it slows down and changes direction, leading the brain to interpret the object as being in a different position than it really is. This effect can give the illusion of increased size, making it important for divers to understand this phenomenon to judge distances accurately and avoid potential hazards while underwater.