Getting under the surface in the Cook Islands

Photography is one of the tools I use to satisfy my curiosity about the natural world. But while 99 percent of my photos are taken from land, more than 70 percent of Earth’s surface is covered by water. Life is short and nobody can see everything, of course, but my choice of subjects had significantly limited my worldview.

It’s a discrepancy that I’ve been trying to resolve off and on over the past decade or so. Just over a year ago, I made my greatest effort yet to explore the world beneath the waves as I explored the lagoons surrounding three of the Cook Islands in the South Pacific.

Photography is all about light and naturally that’s the first thing I noticed. The surface of the water bends the sunlight, projecting the patterns of the ripples onto the ocean floor.

It was also fascinating to me how much the underwater environment changes with depth. Even an inch makes an incredible difference.

In the lagoon on the island of Aitutaki, I found a school of small fish, called insular halfbeak, swimming just under the surface. These tiny fish — just a few inches long — were hard to see against the texture of the water.

Swimming just a bit deeper and it was easy to pick out the low tide line. Coral was abundant in the lagoons. It thrives in shallow water, where sunlight is abundant. The sunlight powers algae, which in turn help the coral grow. But the coral also dies if exposed to air. Often, the top of the coral is a nearly flat surface, reflecting the maximum height it can grow and still be always submerged.

Deeper still, the fish seem to get larger. I encountered a few giant trevally, a truly gargantuan fish that can be as long as I am tall.

Cooperation is also on view. The ocean is home to many famous predators, such as killer whales, sharks, although those big threats don’t make it into the shallow lagoons. Still, there are threats, such as the Pacific reef-heron that would stand at the water’s edge and try to prey on feasting fish.

I found numerous fish that would spend their days clustered into tight balls in hopes that such density would offer some safety. These fish — striped large-eye bream are the ones you primarily see here, would — venture off by themselves to forage at night.

Other times fish would cluster not because of safety, but because they had found coral where there was a particularly good source of food. Here, the sound was striking. It could hear constant clicking noises — the sound of the fishes’ teeth against the hard coral.

There’s still so much more to explore. I snorkeled around just three of the fifteen Cook Islands and even that entire chain of islands is a veritable drop in the bucket of the world’s marine environments. But the trip was a start.

Kevin’s new book, Five Minutes in Nature, collects images and stories about his experiences in the wilderness, curated to help you have deeper encounters of your own. Preview and order it here. Prints of his images are available through LivingWilderness.com. Learn about new work by joining his mailing list.)