The hadal zone isn’t named after Hades – the Greek god of the underworld – for nothing. Starting 6,000 meters (20,000 feet) beneath the waves, this murky deep-sea environment is one of the deadliest habitats on Earth, with pressure levels that would crush a human body in an instant. And yet, an abundance of animals seem to exist rather happily down there. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Down at the bottom of the Mariana Trench , for instance, you can practically hear the snailfish laughing in the face of Hades himself as they shrug off 1,100 atmospheres of pressure without breaking a sweat. By contrast, humans are designed to exist in just one atmosphere of pressure, which is why we feel so comfortable at sea level.

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