Ocean habitats, and how to choose an ocean documentary

The short answer

The ocean is layered by light. Near the surface there is enough sunlight for photosynthesis. Below a few hundred metres, light fades to a faint glow. Deeper still, the only light is made by animals. Each layer has a different cast of life, and each is filmed in a different way. A good ocean documentary tells you which layer you are seeing and how the camera got there.

The layers, from the top

NOAA describes five depth zones in the open ocean:

NOAA’s National Ocean Service notes that light can sometimes be detected down to about 1,000 m, but there is rarely any significant light below 200 m. That boundary matters for viewers: a bright, colourful scene is almost certainly lit by the film crew if it is far below the sunlight zone.

How little we have seen

The ocean covers about 70% of Earth’s surface, and NOAA Ocean Exploration notes that more than 90% of it is deep water, below 200 m. As of April 2026, about 28.7% of the global seafloor had been mapped with modern high-resolution sonar. Explorers have directly seen far less: under 0.001% of the deep-ocean floor. NOAA cites estimates of 700,000 to 1 million ocean species, roughly two-thirds of which may still be undescribed.

Treat claims like “the first footage ever” with care, but do not dismiss them out of hand. In much of the deep sea they can be true.

How ocean footage is gathered

• Divers work mostly in the sunlight zone and the shallowest part of the twilight zone.
• Remotely operated vehicles (ROVs) are tethered robots with lights and cameras. They produce most deep-sea expedition footage.
• Crewed submersibles carry people to depth; the footage often shows the viewport or the vehicle’s own lights.
• Fixed and baited cameras sit on the seafloor and record whatever arrives. Bait changes animal behaviour, so a crowd of scavengers is not a typical scene.
• Aquarium footage shows animals in managed care. It can be excellent for close behaviour, but it is not a wild scene.
• Computer-generated reconstructions are common for animals too rare or too deep to film. They should be labelled as reconstructions.

Checklist: judging an ocean documentary

1. Does it say where and how deep? Credible productions name the region and depth, or show a depth readout.
2. Is the camera platform clear? ROV, diver, fixed camera or aquarium. Each tells you something different about the behaviour you see.
3. Is lighting acknowledged? Below 200 m, any colour you see comes from artificial light.
4. Are reconstructions labelled? Animation and composited scenes should be identified as such.
5. Are scientists or institutions named? Expedition footage normally credits the research vessel, vehicle or programme.
6. Do people keep their distance? NOAA Fisheries recommends staying at least 100 yards from whales and 50 yards from dolphins, seals and sea turtles. It advises never touching, feeding or riding marine mammals or sea turtles. Footage of presenters handling wild marine mammals deserves scepticism.
7. Is the narration modest about motives? Watch for confident claims about what an animal “wants” or “feels”. See our guide to reading animal behaviour.

Using this guide with the catalogue

Use the Oceans category and the Deep sea, Open ocean, Coral reef and Coast & shore habitat filters on the Explore page. Each item’s note says which zone and camera platform it shows, where the publisher states it.