Sunlight Zone (Epipelagic) · 0–200 m Nearly all ocean life and virtually all light live here. Dolphins, sea turtles, and great white sharks hunt in water warmed by the sun.
Ocean Science Essentials
🌈 Where Do the Colors Go?
Water absorbs light color by color. Red vanishes by about 5 m, orange by 10 m, yellow by 20 m, and green by 30 m. Blue travels deepest — which is why the ocean looks blue — but even blue fades to black by roughly 1,000 m, the start of the "midnight zone."
💥 Pressure & Adaptations
Pressure rises by about 1 atmosphere every 10 m — at the bottom of the Mariana Trench it's over 1,000 atmospheres, like balancing 50 jumbo jets on your body. Deep-sea animals survive because they have no air-filled spaces to crush: no swim bladders, flexible bodies, and cells built to resist collapsing.
✨ Why Do They Glow?
Below the sunlight zone, an estimated 90% of animals make their own light — bioluminescence. Anglerfish use it as bait, hatchetfish use it to erase their silhouette from predators below, and squid use it to startle attackers. It's chemistry, not electricity: a reaction between luciferin and oxygen.
🛶 Famous Dives
In 1960, Jacques Piccard and Don Walsh rode the bathyscaphe Trieste to the Challenger Deep — the first humans to reach the ocean's deepest point. Filmmaker James Cameron repeated the feat solo in 2012. In 2019, Victor Vescovo's Five Deeps Expedition became the first to reach the deepest point of all five oceans.