Last January, after a week of unrelenting North Pacific storms, I trekked out to Rialto Beach on Washington's Olympic Peninsula at 6 a.m., when the low king tide had pulled the ocean back a quarter-mile from the usual shoreline. I'd gone looking for sea glass, but 10 minutes in, a park volunteer called me over to a tide pool edge, and pointed out a fist-sized fragment of iridescent red coral wedged between two barnacle-encrusted basalt rocks, half-buried in sand. I'd walked past it three times, assuming it was a piece of discarded plastic wrapper.
That's the thing about Pacific Northwest beachcombing: most people show up looking for the same sandy-shore finds they'd hunt for in California or Florida, and miss the weird, wonderful, hyper-specific treasures tucked into the region's rugged rocky tide pools. The PNW coast is shaped by volcanic basalt, ancient forest driftwood, cold nutrient-dense water, and 10,000+ years of Indigenous coastal stewardship, and the tide pools hold finds you won't see anywhere else in the world.
First, a non-negotiable ethical preamble before you head out: the PNW coast is home to more than two dozen federally recognized tribes whose ancestral lands cover every mile of shoreline from northern California to the top of Washington, plus dozens of protected national parks, wildlife refuges, and marine sanctuaries. Never lift rocks to search for treasures under them (this destroys critical habitat for juvenile crabs, sea stars, and anemones already stressed by ocean warming and acidification), never remove anything attached to a rock or clearly alive, and if you find a fragment that looks like it could be part of an Indigenous midden (ancient shell, stone tool, or cultural artifact pile), leave it exactly where it is and report the find to local park staff or tribal cultural resource departments. Many PNW beaches ban all collection of natural materials entirely, so always check local regulations before pocketing any finds.
Below are the most special, often overlooked tide pool treasures to hunt for on your next PNW beach trip, plus how to spot them and what to do with them if you're allowed to take them home.
Weathered Olympia Oyster Shell Fragments
Most beachcombers ignore the tiny, triangular shells scattered across PNW tide pools, assuming they're just broken bits of common mussel shell. But these are fragments of Ostrea lurida , the native Pacific oyster that sustained coastal Indigenous communities for thousands of years, and whose populations are now being actively restored across the region. Tumbled smooth by decades of wave action, their inner surfaces have a soft, pearly silvery-lavender iridescence you won't find on any other shell. How to identify: Look for fragments no larger than a quarter, with a rough, barnacle-encrusted outer edge and a smooth, pearly inner surface. The rarest fragments have a faint, uniform lavender hue from decades of UV exposure, rather than the bright silver of recently broken shells. Ethical note: Olympia oysters are a protected native species in many PNW areas, so only take fragments that are clearly detached, broken, and washed up in the wrack line---never collect a whole, intact live shell. Upcycling tip: Glue a cluster of 3-4 tumbled fragments to a scrap of reclaimed driftwood for a tiny, understated coastal wall hanging, or use the iridescent inner surface as an inlay for a small resin pendant.
Petrified Driftwood Fragments
The PNW coast is famous for its massive, bleach-blonde driftwood piles, but very few people realize that small fragments of that driftwood can petrify, turning to stone while holding onto their original wood grain. It happens when fallen coastal trees get buried quickly in sand and sediment, and mineral deposits replace the wood fibers over decades or centuries. Most people walk right past these fragments, assuming they're just gray rocks. How to identify: Hold the fragment up to bright light, and you'll see faint, wavy wood grain patterns running through the stone. It will feel lighter than a basalt rock of the same size, and have smooth, rounded edges from wave tumbling. The rarest fragments have visible flecks of quartz or tiny agate deposits trapped in the grain. Ethical note: Only take small, loose fragments from the wrack line---don't dig through driftwood piles to pull out petrified pieces, as those piles are critical shelter for shorebirds, small mammals, and insects. Upcycling tip: Sand the rough edges lightly with fine-grit sandpaper, seal it with a matte natural finish, and use it as a decorative accent on a bookshelf, or drill a small hole to turn it into a rustic keychain.
Weathered Red Coral Fragments
The cold, deep waters off the PNW coast are home to slow-growing red coral (Corallium lauuense ) colonies that are protected by state and federal law---you will never find a living colony in a shallow tide pool, as they live 100+ feet below the surface. But strong winter storms often knock loose small, weathered fragments that wash up on shore, tucked between rocks or tangled in bull kelp. Most people mistake them for pieces of red plastic or broken sea glass. How to identify: The fragment will be a deep, saturated brick red, often with tiny raised bumps from the coral polyps, and feel heavier than sea glass or shell of the same size. If you hold it up to light, it will be slightly translucent, not opaque. Bright, glossy red fragments that look freshly broken are not safe to take---they were likely dislodged recently, and may still be viable if placed back in deep water. The matte, tumbled fragments that have been in the surf for months or years are the ethical finds. Ethical note: Red coral is extremely slow-growing (colonies take hundreds of years to reach harvestable size), so only take small, loose fragments, and never collect more than one or two per trip. Upcycling tip: Polish it with a soft cloth to bring out its deep red hue, set it in a simple silver bezel for a minimalist pendant, or glue it to a slice of driftwood for a tiny desktop display.
Pre-Cracked Thunder Egg Fragments
The Olympic Peninsula's coastal bluffs are full of basalt formations that hide thunder eggs: rough, rock nodules with banded agate, opal, or quartz cores. Storms erode the bluffs, washing small fragments of these thunder eggs down into the tide pools and wrack line. Most people see the rough, gray outer layer and assume they're just unremarkable rocks, but if you find a fragment that's already cracked open, you might catch a glimpse of the smooth, banded interior. How to identify: The outer layer is rough, gray, and looks identical to the surrounding basalt, often with tiny quartz crystals peeking through natural cracks. Pre-cracked fragments will have a smooth, polished interior that ranges from soft cream to deep rust red to pale, milky blue, depending on the mineral deposits inside the original nodule. Ethical note: Never break open larger rocks in the tide pool or bluff area---this is illegal in most national parks, and destroys critical intertidal habitat. Only take small, loose fragments that have already washed free from the rock and into the wrack line. Upcycling tip: Pre-cracked fragments make stunning inlays for wooden jewelry boxes or cutting boards, or you can place them on a windowsill to catch the light and show off the agate core.
Long-Detached Sunflower Sea Star Ossicle Fragments
Sunflower sea stars were once the most iconic resident of PNW tide pools, with 16 arms and bright orange bodies that could grow as wide as a dinner plate. But a mysterious wasting disease has decimated their populations, leaving them critically endangered across their entire range. If you find a small, weathered fragment of a sunflower sea star ossicle (the tiny, hard plates that make up their skeleton) that's clearly been washed up and tumbled for months or years, it's a rare, quiet reminder of the species that once filled these tide pools. How to identify: The ossicles are small, pentagonal or star-shaped, pale orange or brown, and feel slightly waxy, not brittle like plastic. Fresh, bright orange brittle fragments are not safe to take---leave those exactly where you find them, and report them to park staff, as they can help researchers track the remaining sunflower sea star population. Only take fragments that are clearly weathered, tumbled smooth, and have been sitting in the wrack line for a long time. Ethical note: Never disturb a living sunflower sea star, even to take a photo---they are extremely fragile, and stress from handling can kill them. Upcycling tip: Glue a small fragment to a piece of tumbled sea glass or driftwood for a tiny, meaningful keepsake, or place it in a small glass vial as a reminder of the PNW's fragile coastal ecosystems.
Quick PNW Tide Pool Beachcombing Pro Tips
- Hit the beach after a strong winter storm, during a negative low tide or king tide, when the most debris and loose fragments get washed up. Check local tide charts the week before your trip to time your visit perfectly.
- Go early in the morning, before other beachgoers show up to kick sand around and disturb the wrack line where most loose fragments wash up.
- Bring a small mesh bag to carry your finds, so sand and salt water can drain out as you walk.
- Pack out any trash you find while you're combing---PNW beaches regularly accumulate plastic debris from the Pacific Garbage Patch, and every piece of trash you remove helps protect the tide pool ecosystem.
At the end of the day, the best PNW tide pool finds aren't the ones you stuff in your pocket. Even if you walk away with nothing but wet boots and a face full of sea mist, you've spent time in one of the most unique, wild coastal ecosystems on the planet. But if you do spot one of these hidden treasures? Take a photo first, then decide if it's better off staying on the beach for the next person to find. Most of them are more special when they're still part of the coast, after all.