Light and Color Underwater

How water absorbs and scatters light, removing red first and blue last, so colors fade with depth until a dive light restores them.

Water eats light, and it eats the warm colors first. Red is largely absorbed within about 5 m, orange fades next, yellow weakens over the following meters, and by 20 to 30 m the world has settled into blues and greens. That vividly red sponge at 25 m looks brown or gray under natural light, and blood from a scraped knuckle appears green, a classic surprise for new divers.

Water also bends and scatters light. Refraction through your mask makes objects appear about 25 percent larger and closer than they are, and suspended particles scatter the remaining light, reducing contrast and visibility. Light dims quickly with depth too, since a large share of surface sunlight is gone within the first 10 m, which is why deep sites feel dusky even at noon and why overcast days darken a dive dramatically.

The practical fixes are simple: carry a dive light to restore true color on any dive, not just at night, and get close for photography, since every meter of water between lens and subject strips color. Underwater photographers add strobes or red filters for exactly this reason.