The twilight zone of the ocean is a mysterious place. At 200-1000 meters below the surface, it's a tough place to study. That's why, during World War II, people reading sonograms from this zone were perplexed when it looked as if the ocean floor was moving up. Every day. And then back down again before dawn. In this latest installment of Sea Camp, we explore what this historical mystery has to do with the Earth's ability to cycle and store carbon in the ocean's watery depths.

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For this week's Sea Camp, we're diving below the ocean's surface to explore the sunlight zone, the portion of ocean that's 0-200 meters deep. Here, we zoom in on some spineless inhabitants envied for their "superpowers." Marine biologist Drew Harvell tells us about stealthy sea slugs, sea stars with super strength and life-saving sponges.

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Plus, check out the comic we commissioned to accompany this episode!

Want to hear more stories about underwater marvels? Email us and let us know at shortwave@npr.org.

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(Image credit: Roberto Moiola/Sysaworld)