Tide safety: wading, clamming and not getting cut off

The real danger: getting cut off

You’ll hear that the tide comes in “faster than a galloping horse.” On most coasts, that’s a myth. The water usually rises a few inches every ten minutes at most; the danger usually isn’t being outrun.

The problem is something else. On very flat sand or mud, a few inches of rise can cover hundreds of yards. And the water doesn’t advance in a neat line from the sea. It comes in first through the channels, creeks and low spots, which are often behind you, between the bar you’re standing on and the beach.

That’s how people get stranded. You wade across a channel that’s ankle-deep, keep digging on a higher sandbar, and when you look back, that channel is waist-deep and running. The same thing happens with rocks and small islands you can walk to at low tide. On the bayside flats of Cape Cod, where the water pulls far back at low tide, or on the mudflats of Maine, the way back can disappear quickly.

Some places add another hazard. In Alaska’s Turnagain Arm, the glacial silt flats can trap a person’s legs like wet cement, and the tide returns over them. Those flats are best not walked at all.

Why the lowest tides are the riskiest

The tides that draw the biggest crowds are the lowest ones: spring tides around the new and full moon, and especially minus tides, when the water drops below the zero line on the tide chart. In Washington and Oregon, razor clam digs are scheduled around minus tides. In California, tide poolers wait for them all year.

They’re the best time to dig or explore, and also the trickiest. Here’s why. A handy approximation called the rule of twelfths describes how the water rises after low tide:

Hour after low tide	Share of the rise	8-foot range	3-foot range
1st	1/12	0.7 ft	0.25 ft
2nd	2/12	1.3 ft	0.5 ft
3rd	3/12	2.0 ft	0.75 ft
4th	3/12	2.0 ft	0.75 ft
5th	2/12	1.3 ft	0.5 ft
6th	1/12	0.7 ft	0.25 ft

Two things stand out:

• on a big spring tide, the water rises well over twice as fast as on a small neap tide, because it covers more height in about the same six hours;
• the rise starts slowly and then speeds up. The first hour fools people, and by the third and fourth hours the water can climb two feet an hour on a coast with a big range.

On top of that, a very low tide lets you walk farther out, so the trip back is longer. That’s why it’s worth checking where the tide falls in the spring and neap cycle before you go, and what a minus tide means in our guide to chart datum and MLLW.

What to check before you go

Five minutes of planning prevents most close calls:

• The time of low tide for your exact beach, not the nearest harbor. Inside a bay or a tidal river, the tide can run well behind.
• The height of low tide. A minus tide exposes more ground and brings the water back faster.
• The surf. With a swell running, waves reach well beyond the still-water level, especially on rocks.
• Wind and air pressure. With a storm and onshore wind, the water can come in higher and sometimes earlier than the table says. A rough rule is about a centimeter of water (under half an inch) for every millibar the pressure drops.
• Fog and sunset. In fog or after dark, it’s easy to lose sight of the shore. Many fall and winter razor clam digs happen on evening low tides, so bring a good light.

Out on the flats: simple rules

• Go out on the falling tide and follow the water as it recedes.
• Set a turnaround time and stick to it. Start back no later than the time of low tide, and earlier if you’re far out or crossed channels.
• Watch the channels you crossed. They fill first. If the water is above your knees and moving on the way back, don’t cross.
• Be careful with soft mud and sand. If you sink, don’t thrash. Lean back to spread your weight, work your legs out slowly, and call for help.
• Don’t go alone, and tell someone where you’re going and when you’ll be back.
• Carry a charged phone in a waterproof pouch and wear shoes that grip wet rock and seaweed.

Tide pools and rocks: watch the waves

On rocky shores, the bigger risk is usually waves rather than being cut off. As the tide rises, rocks that were dry come within reach of the surf, and waves arrive in sets: a few calm minutes, then three or four much bigger ones. Sneaker waves on the Pacific coast can run far up a beach without warning.

• Watch the sea for a while before you climb down to the rocks.
• Always keep an escape route uphill, and don’t stay on a rock the water can surround.
• Rocks covered in seaweed or green slime are as slippery as ice.
• Never turn your back on the ocean.

If you fish from jetties or rocky points, our guide to tidal currents explains why the water runs hardest at points and inlets.

Clamming: licenses and shellfish safety

Digging clams isn’t a free-for-all. Rules are set by each state, and they vary a lot:

• most states require a shellfish or fishing license for recreational harvest;
• there are size limits, daily limits and sometimes specific open days, like the razor clam digs announced in Washington and Oregon;
• some beds are leased to commercial growers or closed for conservation;
• areas can be closed for pollution after heavy rain or for marine biotoxins, including red tide, and shellfish from a closed area can make you seriously ill even if they look fine.

Before you go, check your state’s fish and wildlife agency for licenses and limits, and its health or agriculture department for current shellfish closures.

If something goes wrong

• Call 911 as soon as you realize you can’t get back, before the water reaches you. The earlier you call, the easier the rescue.
• If you carry a VHF radio, the US Coast Guard monitors channel 16.
• Get to the highest ground nearby and stay visible.
• Don’t try to swim across a channel with current: a tidal current can be stronger than a strong swimmer.

Quick checklist before you hit the beach

1. Time and height of low tide for your exact spot.
2. Spring tide or minus tide? Give yourself even more margin.
3. Surf, wind, pressure and fog.
4. A turnaround time set before you leave.
5. A charged phone, good shoes and someone who knows where you are.
6. Licenses, limits and shellfish closures for your area.

To understand how far the water will move at your beach, the next step is learning how to read a tide chart.