Shane Reynolds (aka Shane O) on Instagram: "Snell’s window is a circular cone of light, about 97 degrees wide, that underwater viewers see as the entire above-water world compressed into one view, caused by light bending (refraction) at the water’s surface, where light entering from outside the cone reflects back into the water, creating a darker, mirror-like border. Named after Willebrord Snell, it acts like a natural fisheye lens, revealing the sky and horizon, but compressing the full 180° pa