Move over, Halloween. It’s Docktober on Puget Sound

Nature lovers often hit the beach at low tide to catch glimpses of underwater life in fleeting tidepools at the margins of Puget Sound. Some nature nerds like to hang off the edge of a dock instead.

About 40 people walked onto the docks of a marina near Olympia, Washington, on a sunny October Sunday, though not for the usual reason of hopping on a boat.

This crew came to get down — on their knees, or even their bellies, for some of the best views into another world.

“You can see all of these skeleton shrimp in there, kind of moving around. But there’s tons of them all over the dock right now,” Luan Roberts of Seattle said while sprawled face down on the floating dock, with her head and shoulders out over the water. Alexander Prescott of Olympia lay next to her as they peered just below the surface.

Throughout the day, Roberts pointed out strange animals living on the underside of the dock for Prescott and others. Some creatures looked like plants, or feather dusters, or butterflies, or skeletons. It was almost like an underwater costume party.

“Oh, wow, yeah. Those are so cool,” Prescott said when he saw the stick-like skeleton shrimp crawling through a bushy patch of hydroids, stationary animals related to sea anemones. “They’re very camouflaged, aren’t they?”

“Yeah, but once you see them you can’t unsee them,” Roberts said. “They’re kind of creepy.”

The tiny predators can change colors like a chameleon and have toxins in their unusually large front claws. Picture a boxer wearing poison gloves.

The horizontal humans were enjoying a relatively obscure hobby known as dock fouling.

“Dock fouling is just exploring what’s living on the dock, seeing what accumulates here,” Roberts said. “It’s kind of like a puzzle, figuring out what’s going on.”

Roberts has dubbed the month “Docktober”: A month dedicated to appreciating and documenting natural wonders that thrive on the infrastructure humans put in the sea.

She has organized dock fouling meetups around Puget Sound.

Why “fouling”? Things that grow on docks and boats have long been considered foul by boaters.

Many boat owners paint their hulls with anti-fouling pesticide paint to keep the vessels clean and moving efficiently through the water. Anti-fouling measures can also help prevent boats from spreading invasive species.

The most popular anti-fouling paint kills by leaching copper, which can kill salmon as well as target species, into the water. Washington state has tried to ban such copper-based boat paints but to little effect. A ban originally scheduled to take effect in 2018, then in 2026, has been postponed indefinitely.

“Somehow we are still not able to find a safer and effective alternative that works as well as copper,” Washington Department of Ecology chemist Iris Deng said.

So-called bio-fouling can even lead to environmental disaster: In 2017, the netting of a fish farm in Skagit County was so clogged with tons of mussels, anemones, and algae that tidal currents tore the farm apart, letting 250,000 non-native Atlantic salmon escape into Puget Sound.

“Fouling is usually a negative term used for boats that have been fouled by barnacles, and that’s a negative. So it’s nice to see it have a positive spin to it,” Prescott said.

Nature lovers might not normally be attracted to maritime parking lots, where oil slicks, pesticide paint, and boaters’ litter can pollute the water, and the air sometimes smells like two-stroke exhaust or creosote. But docks and marinas also provide a sort of unnatural habitat for many life forms.

Luan Roberts says each saltwater dock is “a dance floor of discovery.”

“There’s tons to see,” Roberts said. “The animals seem to just kind of defy all of that for whatever reason. I mean, I’ve seen tons of life even in pretty polluted conditions.”

Dock fouler Sidney Gerst brings a mat to lie on to avoid bird poop and other gunk.

“I like that it is not very difficult to see really cool stuff, and it doesn’t take much effort,” Gerst said. “You just look down, and there’s a whole ton of stuff that you can learn about and see and point out once you do know about it.”

Participants are encouraged to document their finds and upload them to a citizen-science website called iNaturalist to help researchers studying these organisms.

Gerst organized the Olympia-area Docktober event to help people appreciate the diversity of life they are surrounded by.

“I hope people get just kind of a sense of wonder of where we’re at in our world and getting a better understanding of what’s underneath our feet,” Gerst said.

Some attendees have deep expertise and can identify hundreds of species at a glance. Others are brand new to it.

“I just saw something super pretty. It’s like this floating thingy on the surface. I don’t know what it’s called,” Warren Lee said.

He drove down from Seattle for the event after seeing photos of local sea life on social media.

“I saw these very beautiful creatures, and then, yeah, I thought might as well just come check it out,” he said.

Ghader Alrashid of Olympia said she’s been obsessed with marine life ever since seeing her first sea star on the Oregon coast in 2025 and going tide-pooling for the first time in 2026.

“It’s just a whole new world that I wasn’t aware of before,” Alrashid said.

October is an ideal time for dock fouling, according to Roberts. Unlike summertime on Puget Sound, October’s low tides come late at night and are not especially low.

Roberts said, in October, many docks also seem to have an explosion of her favorite creatures — the otherworldly animals known as nudibranchs, or sea slugs.

“It’s their time of year,” she said.

In shallow tide pools, aquatic creatures often shrivel up into droopy blobs to avoid exposure to air or high temperatures. But along floating docks, which are always submerged, many of the most stunning creatures are at their best, showing off all their frilly, floating, even psychedelic mini-majesty.

“I have to show you this very tiny slug. It’s a different species,” Roberts told a visiting reporter.

This one was barely visible to the naked eye. Other Puget Sound “nudis” can be up to a foot long. They come in about every combination of colors, shapes, and textures that Doctor Seuss might be able to dream up.

“They look quite alien and dramatic, and they can have very flashy, bright colors, or I call them magic sprinkles in the slugs because most slugs seem to have like this almost refractive pigmentation,” Roberts said. “They just look very strange.”

On this outing, visitors saw everything from a shag-rug nudibranch to a giant rainbow nudibranch flopping its multicolored way through the water.

Giant rainbow nudibranchs grow up to a foot long, making them one of North America’s largest species, sharing that crown with the orange-peel nudibranch, also found in Northwest waters.

Roberts said she’s been seeing the giant rainbow slugs consistently in the Olympia area for the past five years.

“I’ve been on a hunt to see them. I think they’re called the giant nudibranchs,” Alrashid said after seeing her first-ever nudibranch. “Those were cool to see.”

Roberts encouraged prospective dock foulers to make sure it’s okay with dock owners and to stay out of the way of people using the docks for boating, their primary purpose.

She also asks dock foulers not to blast the locations on social, or public, media, for fear good spots might be overwhelmed, organisms harmed, or permission to go dock fouling prohibited.

Finally, look, but don’t touch the delicate animals that cling to life where humans park their boats.