SDI Open Water Scuba Diver Practice Exam 2025 – Complete Test Prep

When observing objects underwater, they generally appear closer and larger than they actually are when viewed on land. This phenomenon occurs due to the refraction of light as it passes from air into water.

In air, light travels relatively straight, allowing you to perceive distances and sizes accurately. However, when light enters water, it bends, leading to a distortion of perception. For instance, an object that is submerged will appear to be at a shallower depth than it truly is because the light is bending as it moves from the water into your eyes.

The combination of light refraction and the magnifying effect of water makes underwater objects seem larger. This optical effect can result in divers overestimating the size and proximity of objects, which is an essential consideration for safe diving practices and navigation. Understanding this phenomenon is crucial for divers to accurately judge their orientation and distance from objects underwater.