Excerpt and photographs from UNDERWATER WILD by Craig Foster and Ross Frylinck. Copyright © 2018, 2021 by Quivertree Publications. Reprinted by permission of Mariner Books, an imprint of HarperCollins Publishers LLC. All rights reserved.

At spring low tides we would wade through the shallows, carefully lifting up rocks to see what lay hidden beneath them. Under every rock we found an array of tiny living creatures of incredible variety, including glowing worms, tiny rock suckers, and brightly colored nudibranchs, a type of sea slug. Craig also showed me how animals could be tracked by their egg masses. Using a sea hare as our teacher, he showed me how these squidgy animals that look like luminous slugs were always close to their eggs. Whenever we saw the glowing yellow, spaghetti-like mass of eggs, we would soon find the parent hiding close by.

What was most interesting to me was Craig’s fascination with these seemingly insignificant animals. When I questioned him about it, he told me that he found them more compelling than sharks and whales. For someone who had spent a lot of time with some of the largest predators in the sea, this was a very unusual admission. I was somewhat incredulous and couldn’t help wondering if he really meant what he was saying.

Sitting quietly on the rocks together, we also began to observe very interesting animal behavior in the pools. We watched sea anemones wage slow-motion war, lashing each other with toxic stinging cells. On one occasion we observed a large sea star creeping over a rock, chasing fine top-shell snails. As they reached the edge of the rock, instead of gliding over the edge, the snails jumped into the abyss. They left their trails in the sand and then tumbled through the column of water to finally land safely on the sandy floor. Because the sea star has sticky feet, it couldn’t release itself and make the same jump, so the top-shells won a lead.

The new photo book, "Underwater Wild."
Courtesy of Mariners Books

Thinking the chase was over, we noticed that one of the top-shells had landed square on its back in the sand, and no amount of “spinning” its upside-down foot would get it upright. The huge sea star moved ominously down the rock, heading for the trapped mollusk. We thought it was game over for the little animal—but then an amazing thing happened: Another, larger top-shell turned around and allowed the trapped animal to grab its shell and hitch a ride to safety.

The sea star realized that it couldn’t outrun the top-shells, so it turned its attention to a nearby stationary urchin, which had covered itself with an empty limpet shell. The sea star’s arm reared up onto the urchin’s back, clearly moving in for the kill. Its sticky feet grabbed the protective shell, pulling it off the urchin’s back and giving the spiny creature vital seconds to escape. The adjacent urchin was not so lucky, having no protective covering. The sea star easily enveloped it. In the astonishing way sea stars feed, it extruded its stomach and slowly began the process of digesting the urchin externally.

These little rock-pool nature “reality shows” had all the drama of a lion kill in slow motion. It was like watching a psychedelic Star Wars movie in a bowl of seawater. After a day of wandering around, watching, playing, and tracking, we were windblown and tired but felt at peace. The key to getting into this state seemed to be the purposeless way in which the day unfolded.

I thought a bit about purposelessness and how play, by its very nature, is aimless. Watching these small creatures search for their next meals, I began to see that nature has a playful side. I started to think that if we all had the same aimless, playful attitude, then we would be more in sync with Craig’s “original design”.

The saddle-shaped keyhole limplet
It took me a long time to begin to understand the mysterious life of the saddle-shaped keyhole limplet. The animal is slowly losing its shell in the evolutionary process. The shell rides like a small saddle on its back, providing minimal protection from rock suckers and octopuses. So the limpet hides under sand and rocks to protect itself, and pushes a small part of its sticky foot into the water column to catch the floating pieces of seaweed it feeds on. Craig Foster and Ross Frylinck
Top-shell snail trails.
These were some of the first marine tracks I saw: top-shell trails. Most of these sea snails leave an invisible film of slime as they travel over the rock. Fine particles of sand become trapped in slime and reveal the hidden trails. Foraging limplets use these tracks to find their way home. I’ve learned to identify species by the width of their track and the pattern of their movement. Craig Foster and Ross Frylinck
It is possible to track what a young abalone has eaten by looking at the color pattern on its shell.
It is possible to track what a young abalone has eaten by looking at the color pattern on its shell. Representing a very rare case in nature, this animal has kept changing its diet, from bacteria and algal sporelings to kelp and back again. The red is associated with the microbial finds and the blue with the kelp. Shells, and even the bones found in fish heads (called otoliths), leave tracks from the past. Craig Foster and Ross Frylinck
Tracks left by the sea plant, acid weed.
I spent hundreds of hours walking the shoreline learning to track, often alone and sometimes with Ross. For many weeks this strange track had me foxed. Eventually, I realized it had been left by a sea plant named acid weed. The seaweed stores sulfuric acid in its cells, probably to deter feeding herbivores such as urchins and sea snails. Large waves break of the acid week and wash it ashore. When exposed to the air, the seaweed releases sulfuric acid and burns a perfect replica of itself into the algae growing on the rock. The track seen here is very clear because the algae had been burned the day before. It will fade over a couple of weeks as the algae slowly grow back. Craig Foster and Ross Frylinck
A trap limpet waits to slam down on a kelp frond as it washes under its shell.
A trap limpet waits to slam down on a kelp frond as it washes under its shell. Craig Foster and Ross Frylinck
A giant stingray
I approached this giant stingray carefully, letting it see my relaxed posture. I noted tracks left by different mollusks in the fine layer of sand on its wings. They enabled me to calculate approximately how long the ray had been sitting on the sand—in this case, at least one hour. This was part of the giant puzzle of the underwater tracking method I was developing, a way to understand the complex matrix of the Sea Forest. Craig Foster and Ross Frylinck
Cape clawless otters
It’s quite common to see the track of an encounter between a cape clawless otter and a shark. The victim is normally a dark shyshark, and its brain and organs, especially the nutrient-rich liver, are most often eaten, while the ammonia-rich flesh and body are left to the kelp gulls. Our friend Pippa was fortunate enough to photography two adolescent otters sharing a dark shyshark. Unusually, these youngsters ate most of the shark’s flesh too after first eating the organs. Craig Foster and Ross Frylinck
Found sea creature tracks
One of my most interesting tracking experiences was with an otter on a remote rocky beach. For 50 meters I backtracked a set of the strangest prints I’d ever seen. It looked like an artist had painted perfect otter pawprints in black on the rocks. Suddenly the tracks stopped at a large patch of black ink. In my mind I saw the otter coming out of the water with either an octopus or a cuttlefish in its mouth. It ate the cephalopod and dipped its paws in the ink. As it walked away, the otter printed perfect ink tracks on the smooth boulders. I searched under the rocks near the kill site and found a cuttlefish bone with otter tooth marks embedded in it—the final piece of this wonderful tracking puzzle. Craig Foster and Ross Frylinck

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