In dark, greenish water, fish the same mottled gray as the rocks below them make sharp turns or float aimlessly. Sea plants grow from hunks of concrete or metal, the industrial shapes of dock foundations or boat parts covered in barnacles. And suddenly, a blocky geometric dome emerges in the deep, like an underwater greenhouse coated in lumps of plumose anemones shaped like ghostly mushrooms. All this, just feet from a ferry dock.

Scuba diving in Washington may not look anything like the tropical version, with those postcard-ready coral reefs and clownfish—and that clear visibility. But the underwater scene around Seattle thrives thanks to teeming wildlife and some strange things to be found under our sea.

Near where the ferry departs for Whidbey Island, the stretch of Puget Sound is also dotted with pipe stacks, sunken boats, and pilings, all mapped by the scuba divers that like to explore there. Trash, to be sure, but also habitat, says diver and park volunteer coordinator George Barron; there’s “not an inch of the structure that is not covered with life.”

By law, no one is allowed to dump objects in the Sound, for entertainment or otherwise. But once items do end up off the coast of Mukilteo, they become something to explore. The 20-foot-tall geodesic dome made of PVC pipe was placed, Barron thinks, two or three decades ago, and today he spots rockfish and wolf eels—or lingcod many feet long—around it. At one time this area teemed with crab, “so thick that the seafloor appeared to move,” says Barron. This is why he and a group of local divers hope to protect this particular bit of underwater life. The Mukilteo preserve they picture would allow divers but not motorboats, permit photography but restrict fishing. “Leave only footprints,” he says—or fin prints, in this case.

There’s precedent a few miles away, where the Edmonds Underwater Park abuts another ferry terminal. For more than 50 years, it’s been kept as a preserve of sorts, a Marine Protected Area complete with 2.5 miles of underwater nature trails marked by ropes and barriers. The prohibition on fishing or boats in the park helps species thrive—from the tentacled sand anemone to the giant Pacific octopus.

Barron teaches through Underwater Sports, a multilocation dive shop that offers training, gear, and a central hub for Northwest diving. It’s a year-round sport, even as divers don drysuits to deal with the cold. Instructor and underwater photographer Annie Crawley names fall as a favorite season, thanks to visibility. “We call it Divetober for a reason,” she says. “You have these healthy kelp forests, and summer fish and winter fish.”

Some of the region’s most dramatic sights, like a PB4Y bomber that crash-landed in Lake Washington in the 1940s, are so deep as to require technical training to reach. But the Edmonds park sits just 40 feet down, a depth newly certified divers can reach.

Barron’s group is working with Mukilteo city government and notes that local tribes, among others, need to be involved in changing fishing designations. But he envisions Mukilteo as a “seed,” a place that will help salmon to grow, for seagrass to spread, for crab to multiply. And, as a bonus, for the population of local scuba divers to blossom.

Under the Where?

Where to find other Northwest dive sites.

• San Juan Islands
  Divers explore waterways better known for their large marine mammals. Spotting a whale while underwater is rare, but there are plenty of rock formations, eels, crabs, and sea cucumbers.

• Hood Canal
  Giant Pacific octopus and rockfish live in the mild currents among forests of eelgrass deep in this natural fjord. 

• Clear Lake
  Geology and scuba collide in central Oregon, where exceptional underwater visibility shows off a sunken forest created by a lava flow and a spring emerging from basalt.