Twice a week, from the train that runs between Sacramento and Berkeley, I see the force of the Carquinez Strait’s water flowing and eddying under the Benicia-Martinez Bridge, and it is the best part of my commute. On every tide, billions of gallons of water rush from San Pablo Bay into Suisun Bay and back again through this mile-to-half-mile-wide, at points 120-foot-deep, eight-mile-long bottleneck. The tidal current can exceed three knots, walking speed on land but formidable in a small boat. Today, at last, I will see the strait from the water—but I am a little wary.
My partner Wes and I put in at Benicia’s West Ninth Street boat launch a little before a noon high tide. Our sailboat is a 16-foot Wayfarer, a fiberglass dinghy from 1971 that has been mostly languishing in the driveway since we bought it; we haven’t even named it. A while back, Wes and I lived on a small sailboat. Some parts of that life were hard to give up, while others were easy to, and sailing now can bring both to mind. But today we are in a mood to explore new waters. An eight-knot westerly blows through the strait, funneled by the steep hills toward the Delta: enough to get places, but not too frisky. Characteristically, I have forgotten my gloves but remembered the sandwiches. We tighten down the last few lines and shove off.
A strait is a place of motion. Change is a constant in our universe, a fact we humans often struggle with, but certain places are especially good at reminding us of it. The Carquinez Strait itself was only just born, some 560,000 years ago—explosively, according to one theory—when a giant inland lake forced a path to the ocean. This created the unusual inverted river delta (with the fan pointing inland, instead of spreading out onto the coast) that is the San Francisco Bay.
Today, Carquinez Strait is where the coast meets the valley, but the line of engagement between fresh and salt water is always moving, and it even varies vertically in the water column. Bigger freshwater outflows push the salt line westward; humans regulate these flows from January to June. X2, as scientists call the salt line’s daily (and vertical) average, is defined as a distance from the Golden Gate Bridge. Its location is a subject of intense political interest, because it is influenced by the amount of water we Californians use. That’s been true ever since we started damming the rivers and plowing the Delta. The salt line travels around 12 miles on each tidal round trip, and depending on the season and year, X2 ranges within Crockett and some 40 miles upstream to Rio Vista, near the confluence of the Sacramento and San Joaquin rivers.
The C&H Sugar refinery, which opened at Crockett in 1906, produced some early data on the salt line, tracking how far upstream its barges had to go to find fresh water for sugar-making. Nowadays, in a wet spring, fresh water can flow all the way down to the sugar refinery, migratory birds throng the shoreline, and scads of young longfin smelt are swimming around in the strait. Researchers speculate the fish may tend to stay in the fresher side of the salt line to avoid getting eaten by anchovies. In the summer, when the strait is saltier, sailors have occasionally seen porpoises and saltwater jellies.
What happens when a body of salty water meets another, fresher body, coming through the strait? Something has to give: they may mix, or dance in an eddy. Or, in high flows, on an ebb tide, they may go their separate ways. The fresh water is heading downhill to the sea, while the seawater is nosing inland. The denser salt water dives under the fresh water, and any biologists sampling the depths have to take care to tow their net the same direction as the lower layer, lest it crawl beneath the boat.
I dip two fingers into the olive-green water and sample it: mildly salty.
I want to sail closer to the wilder south side’s green glowing hills, where Carquinez Strait Regional Shoreline stretches across grasslands and oak and riparian woodlands. Here, a lacy black grove of eucalyptus trees, killed in a fire; there, hidden in the hills, the town of Port Costa, population 190. A Benicia Yacht Club racer told me how to anchor safely and clamber over the railroad tracks, arriving at dinner like a pirate. But we tack conservatively. The strait’s rocky south side is dotted with rows of worn pilings, the ghosts of old docks. Once these pilings held up Industry. Now they’re perches for pelagic or double-crested cormorants, drying their wings after swimming for their dinners. I’ve seen kayak fishermen wending through here, but for sailors, land is the opposite of safety. A train rumbles through blowing its horn, underscoring the point.
If you can get out on the water, you will see the strait differently. Not as negative space dividing the hills, but as a place in itself. Once floating, you are severed from the world of land people and their land hustles. Even if you see other boats—and there are very few out here, for reasons I cannot fathom—they are unlikely to be helpful when trouble arises. Here, your vessel is your whole world. The air is a force, working with or against you. Your mind fills with the concerns of wind and waves: how they are shifting each moment, the subtle reactions of the boat, whether it is time to tack. Here, nature is in charge. And, fundamentally, on the water, you are alone.
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We sail toward two Canada geese that clearly share this view, expecting us to move rather than the reverse.
“What are they doing?” I say, ducking the dinghy to accommodate them. And then I see: a spring ritual, one atop the other. Lots of splashing. “Oh.”
I’m on a quest: finding one of the 13 or so osprey nests around Mare Island that I saw on a map by Tony Brake, an expert and volunteer with S.F. Bay Ospreys. Ospreys often nest in industrial areas—if it’s a tall thing near water, an osprey will pile sticks on it. They have been taking over the Bay ever since a single nest was spotted at Mare Island in 1990; a 2023 area census found 59 hatchlings in 28 nests. To find them, we zigzag upwind toward San Pablo Bay: first toward the poppy-smeared hills of Dillon Point, then over to the puffing sugar refinery, where we are dwarfed by a bulk carrier’s stern blue cliff of a hull. Now we approach Interstate 80’s twin bridges, on the strait’s west end. Cars and trucks rush overhead—land people, land concerns—while we sail under in the gull-and-tugboat lane. (Western gulls breed on the bridge’s supports, noisily.) Wind does weird, ornery things at bridges; cursing is de rigueur. But here the wind holds, and the current is in our favor.
Wes helms as we approach Mare Island Strait, where the Napa River’s water empties into San Pablo Bay. He doesn’t like to mix binoculars and boating. Scanning, I spy a tall light pole with promising lumps atop it at Mare Island’s south end.
We sail by and confirm its magnificent osprey messiness, a nest overflowing with sticks at least four feet wide. In the spring, a male osprey performs a “sky dance” with dramatic swoops and sometimes a ceremonial fish. Later, he rustles up nest-building materials, while the female does the arranging. Then she lays some cream-to-cinnamon eggs.
On the light pole, a white head pokes up. Hello, osprey!
Just when I am wondering what they are eating, a fish jumps. “Big one!” Wes says. The big dogs here are sturgeon. Too big for osprey—which around here have been seen in recent years eating jacksmelt, striped bass, salmonids, and a singing fish known as the plainfin midshipman. Ospreys dive feet first, unlike some other fish-eating birds, and carry off their prey using the grippy barbed pads on their curved talons.
Osprey craving satisfied, we run downwind back to Benicia. I am admiring the Cal Maritime Academy’s blue-and-gold training ship, the Golden Bear, when the Wayfarer lurches across the water like she has been tossed over a small hill. I look back and see a meaningful riffle. This must be where the waters of the Carquinez and Mare Island straits converge. These flows—with their different salinities, volumes, temperatures, and sediment loads—each affect the other and everything that lives in the Bay. We were in one strait, and now we are in another, and it feels very different. Fish often congregate at such convergence zones, says Wim Kimmerer, a San Francisco State University professor emeritus—though what they are up to is not well known. For us, it is a rude surprise to face the tidal current, now at its fastest, halfway between the tides. But the wind has our backs, literally.
Clouds overtake the sun. Water darkens, wind freshens, waves kick up and froth; mood becomes more serious. Sailing downwind requires less core strength but more concentration than beating upwind, as the boat is less stable. It would be hard kayaking, but the Wayfarer comes to life. We hunch down while watching the waves behind us, to stay on their good side. I needn’t have worried about being able to return. At my back is Mount Tam, ahead is Mount Diablo, and we are flying. I have a name for the boat: Osprey.
GETTING OUT THERE
Explore the Carquinez Strait
Putting in: Public boat launches are at West Ninth Street in Benicia and Martinez Marina; check the Bay Water Trail map for more options.
Birding: “Birding the Carquinez Strait,” by Alvaro Jaramillo, is a wonderful free guide. Learn more about ospreys and see them on webcams at SFBayOspreys.org.
Be aware: Strong tidal currents and fast-changing conditions here are not ideal for beginners. Shallow Southampton Bay is excellent for paddlers, less so for sailboats (especially at low tide). Wrecks are marked with white PVC pipes. Get free NOAA charts online, and learn the hazards and right-of-way rules (an excellent resource is NOAA’s Coast Pilot).
Learn to sail: Schools include Alameda Community Sailing Center, Cal Sailing Club in Berkeley, and Tradewinds Sailing School in Richmond; or check for lessons with area yacht clubs, which vary greatly in price point and vibe. At many clubs, you can show up on the dock before keelboat races and join as crew, even with no experience. Or use the find-a-crew service run by Latitude 38, our local sailing magazine.
By land: By foot or bicycle, explore the 24-mile-loop part of the Carquinez Strait Scenic Loop Trail that rings the strait from bridge to bridge, with fine vistas and some 1,500 feet of elevation change in rolling hills.
