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Rob Cala cautiously sidestepped a tide pool where eddies swirled around anemones, spiky urchins and hermit crabs at Fitzgerald Marine Reserve in Moss Beach.
“What I love to share with people is we’re standing on the bottom of the ocean right now,” the San Mateo County park ranger supervisor said during an especially low tide in early December.
That day, the tide was about a foot or two farther out than normal thanks to a convergence of celestial events: the sun, Earth and moon aligning and the moon reaching its closest position to Earth in its orbit, all while the Earth approaches its closest point to the sun.
The result is a stronger-than-usual gravitational pull on the Earth that causes some of the highest tides — also known as king tides — and lowest tides of the year. They usually occur monthly throughout winter, with the next ones happening Jan. 2-3.
As the king tides reach their peak and creep deeper inland, they exhibit what sea level rise and the threats it poses may look like in the future. But, along with the low tides, they also expose how coastal and estuarine species adapt to extreme changes in their environment. It’s a chance to observe wildlife, including some that are otherwise difficult to see, and learn about their behaviors.
“That’s where that adaptation comes in,” Cala said about the wildlife at Fitzgerald during low tides. “There’s animals out there that are capable of breathing air, or at least resisting desiccating from the sun.”
A red six-rayed sea star crawls around a tide pool at Fitzgerald Marine Reserve on the San Mateo County coast during an exceptionally low tide on Dec. 4, 2025. Photo by Magali Gauthier. 
A sea clown, a type of nudibranch or sea slug, is seen floating in a shallow tide pool at Fitzgerald Marine Reserve. Photo by Magali Gauthier. 
A nudibranch, also called a sea slug, is seen floating in a shallow tide pool at Fitzgerald Marine Reserve. Photo by Magali Gauthier. 
An ochre sea star is seen on the reef at Fitzgerald Marine Reserve. Photo by Magali Gauthier. 
A sea anemone’s tentacles sway in the water in a shallow tide pool at Fitzgerald Marine Reserve. Photo by Magali Gauthier.
Limpets, a type of aquatic sea snail with a conical shell, can hold water in their shells to keep from drying out during low tides. Mussels will close shut to keep moisture in. Anemones out of the water will retract their tentacles and cover themselves in sand.
“It’s like sunscreen — they’re basically just trying to not dry out by exposure,” Cala said. Having worked as a park ranger for 15 years, Cala knows the wildlife intimately and is locally known for his photography of the tide pools and of the coast.
In one shallow pond at the reserve, an ochre sea star tucked itself into a bed of seaweed. Near its center, a cream-colored spot called a madreporite was clearly visible. Sea stars suck water through it into their vascular system to power their movements like gripping and feeding.
All around the star was a constellation of purple sea urchins, turban snails and hermit crabs. Bits of coralline algae, which look pink and crusty when underwater, were turning white and dying from exposure to air during the low tide.
In another tide pool, a group of people took turns peering at an inches-long sea clown, a type of nudibranch or sea slug. It’s easily discernible thanks to the vivid orange markings on its white body.
At the federally protected marine reserve, strict rules are in place to safeguard wildlife. Entering zones designated for the resident harbor seals is prohibited, as are dogs, as they can spread diseases to seals. Visitors shouldn’t run on the reef, as there are slipping and tripping hazards, touch any creatures or remove anything — even abandoned shells.
“Use your eyeballs. Use your cellphone. Take lots of pictures,” Cala said. “Understand that there’s other people treading everywhere. The animals have a resiliency about them because they’re hammered by air, sea, water and predation and everything. But at the same time, with everybody going around and grabbing everything, that can create a lot of problems.”
On the other side of the Peninsula, Aja Yee, a programs coordinator at the San Francisco Bay Wildlife Society, echoed the need to give animals plenty of space when they come closer to shore during these tide events.
The San Francisco Bay Wildlife Society, a nonprofit partnered with the U.S. Fish & Wildlife Service and also referred to as a “friends group,” assists USFWS with research, public outreach and education in its wildlife refuges in and around the Bay Area, including the Don Edwards San Francisco Bay National Wildlife Refuge.
“When it is high tide, you know, they say give your distance,” Yee said. “Give these animals some distance. They’re not usually coming up to this place.”
Around the Dumbarton Bridge, a number of ponds for waterfowl are part of the refuge. On the bridge’s north side, the Ravenswood Trail was closed for duck hunting season, but northern pintails were diving for snacks right on the road’s edge.
The animals were closer than they typically would be due to high water levels caused by the king tide. No binoculars were needed to spot a male pintail’s characteristic long, dark tail sticking straight out of the water while its other half was submerged.
Northern shovelers floated about and could be easily distinguished from mallards. Both species have bright green heads, but the shoveler’s long curved bill was unmistakable.
A rehabilitated marsh that was once an evaporation pond used for salt production is separated from the Bay by a levee on the south side of the bridge. Water levels here are controlled and tidal fluctuations are minimal, so the water was only a little higher than it usually is.
Still, birds were hunting for food within view of the trail. Egrets nipped at each other as they competed for limited space on the narrow bank. A few Forster’s terns hovered above the surface before tucking their wings and diving into the water in a flash. Amid all the action, a bat ray circled the area, its fins breaching the surface every few seconds.
On the Bayside, water levels were significantly higher than usual and the bank was fully submerged, covering wide swaths of pickleweed, a native low-growing shrub with red tips. A great egret balanced on a log bobbing against a water gate as it tried to snap up fish from the rushing waters.
“It can swim. It flies,” Yee said of the great egret. “But it doesn’t usually hang out in a big pond of water like a duck. It’s not designed to sit there in the water and paddle around it. It’s designed to stand at the water’s edge with its long legs and then find its prey and pick it out of the water.”
The Bay’s wetlands are also home to the endangered Ridgway’s rail and the salt-marsh harvest mouse (though none live in this specific part of the refuge). These rare species prefer to hide deep in the low-lying Bay plants. The king tides can force the animals to higher ground, exposing them to people, dogs and predators.
Back on the coast at Fitzgerald Marine Reserve, hushed whispers rose as a red octopus the size of a human palm was spotted crawling right next to someone’s foot. The light was fading as the sun set, and the octopus was nearly indistinguishable from the color of the rock.
Cala said the creatures are known to slither across the reef during low tide, “presumably looking for food.” The creature hid under a large bundle of seaweed as a group of nature enthusiasts eagerly tried to catch a glimpse of it.
A short time later, cheers erupted close by. A red six-rayed sea star, along with another nudibranch, had been sighted.
“There’s spots you can sit and watch and the animals start to reveal themselves,” Cala said. “It’s very meditative, actually.”
Hot spots and approximate timings for highest and lowest tides
Tide predictions can be found at the National Oceanic and Atmospheric Administration website.
Pillar Point in Half Moon Bay (and the nearby Fitzgerald Marine Reserve in Moss Beach)
Jan. 1 highest tide: 6.99 feet expected around 7:45 a.m.
Jan. 1 lowest tide: -1.57 feet expected around 3:20 p.m.
Jan. 2 highest tide: 7.16 feet expected around 8:40 a.m.
Jan. 2 lowest tide: -1.79 feet expected around 4:10 p.m.
Jan. 3 highest tide: 7.14 feet expected around 9:30 a.m.
Jan. 3 lowest tide: -1.77 feet expected around 5 p.m.
Oyster Point Marina/Park in South San Francisco
Jan. 1 highest tide: 8.67 feet expected around 9:20 a.m.
Jan. 1 lowest tide: -1.43 feet expected around 4:55 p.m.
Jan. 2 highest tide: 8.81 feet expected around 10:15 a.m.
Jan. 2 lowest tide: -1.66 feet expected around 5:40 p.m.
Jan. 3 highest tide: 8.77 feet expected around 11:10 a.m.
Jan. 3 lowest tide: -1.68 feet expected around 6:40 p.m.
Palo Alto Baylands
Jan. 1 highest tide: 9.44 feet expected around 9:40 a.m.
Jan. 1 lowest tide: -0.97 feet expected around 6:10 p.m.
Jan. 2 highest tide: 9.60 feet expected around 10:30 a.m.
Jan. 2 lowest tide: -1.13 feet expected around 6:55 p.m.
Jan. 3 highest tide: 9.55 feet expected around 11:25 a.m.
Jan. 3 lowest tide: -1.14 feet expected around 7:45 p.m.
Coyote Point Recreation Area in San Mateo
Jan. 1 highest tide: 9.09 feet expected around 9:20 a.m.
Jan. 1 lowest tide: -1.44 feet expected around 5 p.m.
Jan. 2 highest tide: 9.24 feet expected around 10:15 a.m.
Jan. 2 lowest tide: -1.68 feet expected around 5:50 p.m.
Jan. 3 highest tide: 9.19 feet expected around 11:10 a.m.
Jan. 3 lowest tide: -1.70 feet expected around 6:35 p.m.
Upcoming king tides events
Keep an eye on the event pages for Palo Alto-based Environmental Volunteers and California State Parks, as they previously have held king tides guided walks.
Jan. 2, 10 a.m.-12:30 p.m. Midpeninsula Regional Open Space District docents will lead a walk on the Bay Trail at Ravenswood Preserve and discuss how the king tides impact the marsh, the ongoing restoration of these wetlands and the species that inhabit them. More information can be found here.
Jan. 2, 3 p.m. California State Parks will lead a guided tour of the tide pools at Pigeon Point Light Station State Historic Park in Pescadero, where the tide will nearly reach -2 feet. More information can be found here.
Jan. 3, 11 a.m.-noon The San Francisco Bay Wildlife Society is hosting a guided walk at Don Edwards San Francisco Bay National Wildlife Refuge’s Ravenswood Unit. Attendees can expect to hear about how king tides can give us a glimpse into sea level rise. More information can be found here.
Jan. 3, 11 a.m.-noon The San Francisco Bay Wildlife Society is also hosting a guided walk at Don Edwards San Francisco Bay National Wildlife Refuge’s Alviso Unit. Similarly to the Ravenswood event, attendees can expect to hear about the high tides, sea level rise and habitat restoration. More information can be found here.
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