Dive into this compelling, content‑rich nonfiction picture book and find yourself on an underwater adventure: a marine mission that takes you past reefs, beyond the near‑shore sea floor, down, down, down through the sunlight layer, the twilight layer, the midnight zone-all the way (as in seven miles!) down to the bottom of the ocean!

Keep your eyes peeled-if you're lucky, you might see a 400-year-old shark, a dumbo octopus, or . . . a xenophyophore! Layer by layer, you will get to know all of the mysterious sea life that dwells in the deepest depths while finding out just how interconnected-and crucial-the ocean's ecosystems really are.