Under the ocean exists an entire world, totally separate from our own. Millions of different creatures that look and act nothing like us live out their entire lives in this dark, vast, alien environment that we're barely aware of.
Picture a spot deep in the ocean where the light from the surface can barely reach. In that deep, dark place is a small reef, and reaching up from that reef is a single piece of coral.
Adapted from the "Dwellers of the Deep" test in Kokology 2 by Tadahiko Nagao and Isamu Saito.