Crabby Characters: Stories from the Seafloor

Thom Robbins | story and pictures

Spend enough time beneath the surface of Hood Canal, and the silence starts to speak not in words, but in motion. Everything down there moves slower in the cold except the crabs. The crabs are always busy. Always urgent. I’ve watched one spend ten full minutes excavating a hole no deeper than a coin is thick, only to abandon it and scuttle off as if remembering something more important. One squared off with its own reflection in my camera dome, claws raised like a boxer waiting for the bell. And another cleaned algae off its shell, as if preparing for a first date.

They aren’t graceful like the kelp fish or hypnotic like moon jellies. They’re rough-edged little bulldozers, powered by instinct and old armor, constantly on patrol. You’ll find them under ledges, in discarded cans, perched on the pilings of a long-lost dock. Red Rock crabs, kelp crabs, decorator crabs, hermits dragging their spiral shells like tiny trailers behind them, all of them crawling, shoving, digging, sparring, eating, surviving.

To dive in Hood Canal is to enter their world, not as an observer but as a trespasser in a busy kingdom. And the deeper you go, the more you start to wonder: who’s really watching who?

There are over thirty species of crab living in the Salish Sea, and I swear I’ve startled half of them just getting my fins on. Big ones, small ones, legs like knitting needles—some so camouflaged they vanish if you look away. They're not background players down here. They're the quiet architects of the seafloor. Scavengers, cleaners, prey, and predators, they keep the submerged machine running.

Take the Dungeness crab. Everyone knows that name from a dinner menu, but out here, in the cold green quiet, you see the other side of it. These are not docile creatures. They fight like boxers in the sand, claw-to-claw. I once watched two square off over a fish head, each strike spraying up little clouds of silt. No hesitation, no mercy. The winner dragged the prize beneath a ledge and vanished. The loser waited a few beats, then started digging like it had never happened.

Red Rock crabs are the neighborhood bruisers, bad-tempered, road-shouldered, all edge. Their claws are darker than blood, twice as quick.  You don’t want to get too close. They make sure you know when you’ve stayed too long.

Then there are the kelp crabs, graceful, spindly, with legs that seem to unfold forever. They cling to the long, swaying forests of bull kelp like sentries, their shells often coated in fuzz or film. I’ve seen them frozen in place for minutes, like a spider in a web—until they move. And when they do, they move fast.

But my favorite? The decorators. They’re the mad geniuses of the crab world—slow-moving and soft-shelled, but never unprepared. They tear pieces of sponge and algae from their surroundings, stitching them onto their backs like makeshift armor or fancy hats. Sometimes they vanish into the scenery. Other times, they look like moss-covered monsters crawling across the sand.  I found one once with an entire anemone riding on its back, swaying as a crown.

Crabs do more than scuttle around at our feet. They oxygenate sediment, recycle waste, and form the base of countless food webs. Otters eat them. Octopuses hunt them. Even gulls have learned to flip them over like breakfast pancakes. But somehow, they endure.

Out here, beneath the weight of the water, they don’t feel small at all. They seem ancient, as if they’ve been here longer than we have. As if they know something we don’t, and maybe they do. Watch them long enough and you start to see why: crabs are built like tanks, only stranger. You don’t realize how alien they are until you’re face-to-face with one in the dark, thirty feet down. Your dive light catches the gleam off that hard, unblinking shell. They look back with stalked eyes, unmoving, weighing whether to run, fight, or decide you aren’t worth the thought.

Like spiders and shrimp, crabs are arthropods wrapped in an exoskeleton that is both armor and skeleton, with no bones inside and everything important protected on the outside. That shell, or carapace, is tough as old fiberglass, etched like a puzzle box, often scarred from past fights, and it doesn’t grow with them. When they get too big for it, they crack it open like a coffin and climb out soft and defenseless until the new shell hardens. I’ve found husks underwater that look like dead crabs until you realize they’re ghosts on the sand.

Most crabs have ten limbs, eight legs, and two claws, but don’t let the symmetry fool you. Those claws aren’t there just for show. They’re everything. I’ve watched crabs use them like tools, snapping open clam shells with surgical efficiency. I’ve seen them fight, claws locked like wrestlers on a mat, each trying to twist the other into submission. And once, on a night dive near an old piling field, I caught sight of a male crab slowly waving one claw back and forth in the beam of my flashlight, rhythmic, almost elegant, like conducting the tide. Mating display. Or maybe a warning. Hard to say. But whatever it was, it felt old. Practiced.

Even the Puget Sound king crab, the largest crab you’re likely to see in the Pacific Northwest, with a carapace that can span nearly a foot across, is unforgettable when you’re lucky enough to spot one. Its shell flashes red-orange under your dive light, edged with faint blue highlights as if brushed with frost. 

Sometimes, you’ll notice asymmetry in its claws, with one noticeably larger than the other. This can happen after a molt, when a lost claw is still regrowing, or from years of favoring one claw over the other, like a boxer’s strong hand. That imbalance isn’t clumsy, it’s deliberate. Bigger doesn’t always mean better, but it does mean louder. That oversized claw speaks before the crab ever moves. It says: I’ve survived something you haven’t. I’ve fought. I’ve rebuilt.

Many of them have. Crabs here lose claws to predators, traps, and each other, but they don’t stay broken. They molt, wait, and grow it back slower, a little different, but the same. When you see that heavy claw raised like a crooked banner, it’s not just a weapon, it’s a story of survival, hard-won and costly.

Down here, everything fights to keep going—sometimes with teeth, sometimes with venom. Crabs fight with whatever they’ve got left, rebuilding one joint, one muscle fiber at a time. There’s an honesty in that brutality.

You never forget the first time you see a crab run. It’s not a graceful thing. Not smooth like a seal gliding past or a school of herring flickering in unison. It’s sharp. Sudden. Like something went off inside it. One second it’s there, perfectly still, and the next it’s gone—vanished sideways into the shadow of a rock or beneath a curtain of eelgrass.

That sideways sprint comes from design. A crab’s legs hinge on the sides, not underneath like ours. Each leg pushes like an oar, catching the bottom and shoving the body across the sand with precision. When you see it up close, there’s a rhythm to it, like a dancer on a single beat.

And when they move, they move faster than you'd think. The crabs here in Hood Canal—Red Rock, Dungeness, and the occasional Northern Kelp Crab aren’t built for land speed, but underwater? They’re spring-loaded traps. One second, they’re still, blending into sand or clinging to a piling; the next, gone. Just a blur of motion and a trail of stirred-up silt.

I’ve watched a Dungeness bolt sideways across a sandy shelf with such force it left a trench behind, vanishing beneath a ledge before I could even lift my camera. Kelp crabs don’t move quite as fast, but when they do, it’s sudden, those long, delicate legs pulling their mossy bodies up and over kelp blades like they’re trying to escape the light. Helmet crabs and graceful kelp crabs can vanish into the gloom in a blink if you come too close.

They don’t waste energy, every movement counts. When they go, it’s all at once, like something spooked in the woods, sharp and armed.

I’ve chased more than a few across the bottom camera in hand, bubbles rising just trying to land one clean shot. But more often than not, all I’m left with is a cloud of sand and a shape disappearing into shadow. That’s the game—they always win.

Not all of them run. Some freeze, legs tucked tight, trusting camouflage to outlast your curiosity. Decorator crabs are masters of this—covered in algae, sponges, and stitched-on debris, they hold so still you doubt they were ever moving at all. You notice them only when they twitch once, like something from a dream that leaves no footprints.

Others bluff. The Red Rock raises its claws in defiance, even when outmatched, daring you to come closer. And I’ve seen graceful kelp crabs pull themselves into near-vertical poses, legs extended, trying to look bigger. They don’t want to fight, but they’ll make you think.

Then there are the burrowers, smaller crabs like helmet crabs or hairy shore crabs. When spooked, they vanish downward instead of outward, kicking up sand as they wedge themselves under rocks or into old clam holes. They disappear.

Every crab makes a decision in that split second before it moves: fight, freeze, flee, or fade.  They don’t choose wrong more than once. Here, hesitation means you get eaten. And if you’re lucky and quiet, you get to watch them make their choice. When they stop—when they finally wedge themselves beneath a rock or vanish into the reef’s contours—they don’t pant or pulse like a fish might. They just stop, as if nothing ever happened.

Down here, it’s not the fastest creature that survives. It’s the one that knows when to run, how to vanish, and what angle to take when it does. Crabs figured that out a long time ago.

The eyes are the first thing you notice, two dark marbles on stalks, swiveling like radar dishes in the murk. They move independently, scanning front and back at the same time, and it’s unsettling in a way I can’t quite shake. I’ve knelt in the silt, barely breathing, and watched a crab watch me, one eye fixed on my mask while the other seemed to scan the reef behind it, like it was calculating the best escape route. Or maybe waiting to see what I’d do next.

But crabs aren’t just watching. They’re communicating in ways most people never notice. They tap, drum, raise, and wave their claws in deliberate patterns, not just to warn or threaten but to talk. Males might flash their chelae, the front claws built like living pliers—part weapon, part tool—each ending in a sharp, hinged pincer. Look at me. I’m strong. I’m ready. Don’t come any closer. It’s a kind of semaphore, silent and specific, evolved not for show but for survival. Some species send messages through the seafloor by drumming with their legs.

The closer you look, the more the body itself becomes a language.

Beneath that armored face, their mouthparts are hidden in plain sight, tucked up under the shell like something secret. Most people never notice them. But divers have time. We wait. We watch. And if you’re patient, you’ll see those tiny, feathered appendages in constant motion, pulling in food, sorting it, filtering it, working like a factory line. It’s never still. Even when a crab looks motionless, it’s chewing through the world one particle at a time.

And they’re not picky. Crabs are opportunistic feeders—algae, plankton, fish scraps, rotting kelp, even other crabs if the tide turns cruel. I’ve seen it happen fast, almost clinical. No ceremony. No malice. Just need.

They speak through motion, posture, and action, enough where sound doesn’t carry and light doesn’t last.

Beneath the shell, hidden to most, lies one of the weirdest parts of crab biology: they breathe through gills, just like fish. The gills are tucked into chambers beneath the carapace, kept moist by leg movements and flaps called scaphognathites that pump water over them.  I’ve seen crabs dug into damp sand during low tide, perfectly still but alive, waiting for the tide to return.

Here's something most folks don't realize: you can tell male and female crabs apart by flipping them over. Males have a narrow, pointed abdominal flap; females have a broad, rounded one shaped like a dome. That’s where they carry their eggs, thousands packed tight like orange caviar, gently fanned with back legs to keep oxygen flowing. It’s a strange kind of tenderness, watching it happen underwater. There’s something ancient about it. Something careful.

When you see a crab crawling across the bottom, it’s easy to think of it as just another bit of marine clutter, another scuttling shape in the gloom. But inside that shell is a creature perfectly engineered for survival, part armor, part instinct, part mystery. The more time I spend with them, the more I believe they’re not just part of the seafloor. They are the seafloor, living, crawling, biting proof that nature doesn’t waste time on beauty when function works better.

And still, somehow, they're beautiful.

Crabs aren’t just skittering distractions; they’re survivors in a complex life cycle that begins as floating larvae barely bigger than plankton. After hatching, young crabs go through multiple molts, shedding their exoskeletons to grow. These larval forms, called zoeae, drift with the currents—tiny, vulnerable—before settling to the bottom where the real battles begin.

Molting continues in adulthood. During these soft-shelled interludes, crabs are most vulnerable. Many hide in the sand or under rocks. For females, it’s the only time they can mate, making it a moment of both risk and opportunity.

Once fertilized, females carry eggs on their undersides like a clutch of orange grapes. Watching a crab fan her eggs with rhythmic leg flicks reminds you that even armored creatures tend their young with surprising delicacy.

Not all eggs survive, and not all crabs do either. For every empty shell tumbling in the current, another waits just out of view, ready to take its place.

As a diver, I’ve learned that the best moments often happen in the periphery. You come for the wolf eel or the octopus, but you stay because something small scuttles in and steals the show. Crabs are like that, endlessly watchable, hard-wired to move, eat, and thrive.

Next time you’re under the surface or in a tidepool, watch a crab at work. There’s a world in those legs, strange and alive as anything in the sea. A reminder, we’re only visitors in their kingdom.

Thom Robbins Bio

I am fascinated with the underwater world here in the Pacific Northwest. I have been a diver for over thirty years and have never been happier than underwater with a camera. I spend as much time underwater as possible, writing, shooting pictures, or teaching diving and photography. You can learn more about me at https://www.thomrobbins.com. 

When not diving, I spend time with my wonderful, patient wife, Barb. We live in Shelton, Washington, where we relish a relaxed lifestyle close to world-class diving spots. Barb’s support has been instrumental in my passion for diving; she is my best and often harshest critic, constantly pushing me to capture better photos. Our 21-year-old son inspires me to be a better person every day. Completing our family are our two English Bulldogs, who bring us endless joy.