It’s dark. It’s vast. And it’s the home of countless creatures that are as strange as they are mesmerizing, but they are all uniquely adapted to life at the very limit of sunlight in the ocean. The twilight zone is a critical part of our ocean—yet because it is so remote and inhospitable to humans, scientists have not yet been able to study it in detail. Woods Hole Oceanographic Institution's (WHOI) Ocean Twilight Zone Project is on a mission to expand knowledge of the zone: to discover more about its creatures, their behavior, their place in global food webs, and the important role they play in regulating Earth’s climate.

Photographer Paul Caiger was a postdoctoral investigator at the Woods Hole Oceanographic Institution from 2018-2020 in the Ocean Twilight Zone Project and in the lab overseen by WHOI fish ecologist Joel Llopiz. While there, he focused on acoustic ecology and the life history and behavior of twilight zone fishes. His photographs have become a critical part of the Ocean Twilight Zone Project’s efforts to convey the beauty and mystery of life deep beneath the surface.