How the Moon Controls Tides: A Guide to Spring, Neap, and King Tides

HOW LUNAR RYTHMS SUSTAIN THE LOWCOUNTRY’S MARSH, WILDLIFE AND WAY OF LIFE

STORY + PHOTOGRAPHY BY AUDREY GEIB

Every day the moon pushes and pulls the Atlantic, carving out beaches, guiding fish and shaping the lives of those who call the coast home. Tides rise and fall because of the gravitational forces of the moon and sun. Roughly every six hours the ocean swells inland and then retreats, creating a predictable pattern of high and low tides.The severity of these shifts depends on the moon’s phase. During a full or new moon, the sun, moon and Earth align, producing the highest tides, known as spring tides, which happen roughly every 15 days. A king tide is an unusually high spring tide that occurs a few times a year when the moon is at its closest point to Earth (perigee) and/or when the Earth is at its closest point to the sun (perihelion). Conversely, when the moon is in its first or third quarter, the sun and moon pull from different angles, creating the month’s lowest tides, called neap tides.

RISE AND FALL These two photos, taken just steps from Hudson’s Seafood House on the Docks, capture the swing between high and low tide. In the above photo Skull Creek pushes right up to the rocks, lapping at the shoreline, with hardly any marsh grass in sight. Hours later, the photo to the left shows a completely different landscape: the water has drained away, exposing oyster beds, mud flats and long fingers of spartina grass. It’s a striking reminder of how quickly the tides reshape the Lowcountry’s edges and why locals keep one eye on the water when planning their day.

Shifting sands

For beach goers, tides might mean a shorter walk across sand or a wider stretch for biking. But for the animals of Hilton Head, the daily rhythm is essential. Amber Kuehn, local marine biologist and executive director of Sea Turtle Patrol Hilton Head Island, said every high tide carries in nutrients and small creatures, while every low tide pulls material back out, constantly refreshing the marsh.Without this flushing, marsh crabs couldn’t open their burrows to release gases and aerate the soil, a process that fuels the growth of Spartina grass. The tide also carries out dead reeds from the grass which wash onto beaches, where sand piles around them to form dunes that protect the island.

SAND, SURF AND CYCLES These two photos from Coligny Beach highlight just how much the tides change the shoreline. At high tide the ocean waves roll in strong and steady, perfect for splashing and body surfing, but leave little room for beach chairs. By low tide the ocean has pulled back, revealing wide stretches of hard-packed sand that locals love for long beach walks and bike rides. Same spot, two completely different beach experiences, all shaped by the moon’s pull.

Beachgoer’s tide chart

Even for casual visitors, tides can shape the perfect beach day. At low tide wide expanses of firm sand invite walking, biking or shell hunting. At high tide the water presses close, leaving less space for chairs, umbrellas and play.“A lot of people don’t realize just how different the beach looks at high versus low tide until they see it for themselves,” said Nick Cargo, lifelong local and owner of Cross Island Bike Rental.Staying aware of tide schedules prevents towels from getting washed out and helps families plan better. Cargo said a little preparation goes a long way: waves are best just after high tide, while skim boarders find their stride at low tide on long stretches of glassy sand.

Fishing by the tides

For charter captains Donovon McCoy and John Werner, tides determine where and how they fish.“Redfish are our bread and butter,” McCoy said. “You can catch them every day of the year, just in different ways.”The key is moving water. When the tide is coming in or going out, bait moves with it, and where bait goes, the fish follow.“You definitely want some current,” he explained. “Whenever the tide is slack, you can still catch fish, but it’s not as good.”Werner agreed, noting that slack tide makes fishing harder because less food is carried to the fish. Moon phases also matter; full and new moons bring dramatic spring tides with stronger currents, while neap tides are calmer and easier to fish since anglers aren’t battling large swells.“Those are fun times to fish because you’re not competing with all those big currents,” Werner said. “You get a lot more time to fish certain things, more than you would if it were a really big tide, because there is not as much water moving.”Nature’s fishermen follow the same cues. Dolphins, for instance, often wait at the marsh edge during an outgoing tide, snatching up young fish as they are flushed out of their hiding places within the grass.

The heart of the Lowcountry

The steady rise and fall of the tides is what keeps Hilton Head’s ecosystem thriving, sustaining everything from marsh crabs to dolphins. Werner described it in human terms, comparing Spartina grass to skin and oyster beds to bone structure, with the tides themselves serving as the heartbeat.“Two high tides and two low tides a day,” he said. “It’s a self-cleansing environment. That’s the most amazing thing about Hilton Head. That’s the heart of it, the heart of everything around here. It’s tides.”Whether you’re casting a line, setting up a beach chair or watching the marsh grass sway, the tides are always in motion, and life in the Lowcountry moves with them.

HOW TIDES WORK This image illustrates how the alignment of the sun, moon and Earth shapes our tides. During a new or full moon, their gravitational pull combines to produce spring tides with the most extreme highs and lows. At the first and third quarter moons, the sun and moon pull from different angles, resulting in neap tides when the difference between high and low is at its smallest. These repeating cycles drive the daily rhythm of the ocean, constantly reshaping coastlines and sustaining life in tidal marches.

KNOW YOUR TIDES The moon’s pull doesn’t play favorites. Some days it tugs a little harder, other days not so much and the results shape everything from fishing trips to beach walks. Here’s a quick look at the main players in the tide cycle, each with its own rhythm and impact on Lowcountry life.

Spring tide

King tide

Neap tide

Flood tide

What it is: Water moving in, pushing higher on the shore and into the marsh.

Why it matters: Redfish slip into the grass to feed, and kayakers can glide into spots that are bone-dry at low tide.

Tide tidbit: On warm summer evenings, watch for “tailing redfish.” Their fins flick above the grass as they root around for food.

Ebb tide

What it is: Water draining out, exposing mud flats and oyster beds.

Why it matters: Dolphins often line up at creek mouths during an ebb, snatching fish flushed out of the marsh.

Tide tidbit: The word “ebb” comes from Old English ebba, meaning “receding.”

Slack tide