Depths
Scroll down to go down. Oceanographers divide open water into layers by how much light reaches them; the boundaries are conventions, and animals cross them freely.
Sunlight zone
Enough light for photosynthesis, so nearly all the ocean's plant life is here, and most of the animals people recognise.
- Atlantic bluefin tuna and other fast hunters
- North Atlantic right whales, skimming for copepods
- Leatherback turtles following jellyfish blooms
- Portuguese man o' war at the very surface
Twilight zone
Light fades to a dim blue and photosynthesis stops. Many animals here rise towards the surface every night to feed and sink again before dawn, the largest daily migration on the planet.
- Lanternfish, with rows of light organs along the belly
- Swordfish diving after squid by day
- Hatchetfish, thin as a coin and silvered like a mirror
Midnight zone
No sunlight at all. The water is a few degrees above freezing and the only light is made by the animals themselves.
- Anglerfish, luring prey with a glowing filament
- Greenland sharks cruising the cold slopes
- Sperm whales, visiting on dives that last over an hour
- Gulper eels, mostly mouth
Abyss
Most of the Atlantic floor lies here: wide plains of fine sediment under enormous pressure. Food arrives as a slow fall of particles from above.
- Sea cucumbers, the most common large animals of the plain
- Tripod fish, standing on long fin rays to wait for prey
- Brittle stars and glass sponges
Trenches
Only the deepest trenches reach this far. In the Atlantic that means chiefly the Puerto Rico Trench, north of the island it is named for.
- Amphipods, small scavenging crustaceans
- Snailfish, among the deepest-living fish known