Understanding Tides: A Beginner's Guide

What Are Tides?

If you have spent any time at the beach, you have noticed that the water level changes throughout the day. Sometimes the waves reach far up the sand; other times, the water pulls back to reveal tide pools, rocks, and sea creatures. This daily rise and fall of the ocean is called the tide.

But what causes it? The answer lies 238,900 miles away — on the Moon.

The Moon's Gravitational Pull

Tides are caused primarily by the gravitational pull of the Moon on Earth's oceans. Even though the Moon is far away, its gravity is strong enough to pull the ocean water toward it, creating a bulge of water on the side of Earth facing the Moon.

At the same time, on the opposite side of Earth, another bulge forms. This happens because the Earth itself is being pulled toward the Moon, leaving the water on the far side "behind." The result: two high tides and two low tides every day.

The Sun also affects tides, but because it is much farther away, its influence is about half that of the Moon.

Types of Tides

High Tide

When your part of the coast rotates to face the Moon (or is directly opposite it), the water level rises. This is high tide. The ocean pushes further up the beach, covering rocks and tide pools.

Low Tide

Between the two high tides, the water level drops. This is low tide. The ocean pulls back, exposing tide pools, rocky reefs, and sandy flats that are usually underwater. Low tide is the best time for tide pooling!

Spring Tides (Extra High and Low)

About twice a month, when the Sun and Moon align (during full moon and new moon), their gravitational forces combine. This creates spring tides — extra-high high tides and extra-low low tides. The name has nothing to do with the season; it comes from an old word meaning "to spring forth."

Neap Tides (Moderate)

When the Sun and Moon are at right angles to each other (during quarter moons), their forces partially cancel out. This creates neap tides — more moderate highs and lows with less dramatic changes.

Why Tides Matter

For Marine Life

Tides create one of Earth's most dynamic habitats: the intertidal zone. Creatures that live here — sea anemones, mussels, crabs, sea stars — must survive being underwater during high tide and exposed to air during low tide. They are some of the toughest organisms on the planet.

For Beach Activities

Understanding tides helps you plan beach activities:

• Tide pooling — Best at low tide, especially during spring tides
• Surfing — Tide affects wave shape and break points
• Beach cleanups — Low tide exposes more beach to clean
• Swimming — Be aware of changing water depth and currents

For Coastal Safety

Tides affect ocean currents, including rip currents. Understanding when tides are changing can help you stay safe in the water. Never turn your back on the ocean, and always check tide predictions before exploring rocky areas.

How to Read a Tide Chart

A tide chart shows predicted water levels over time. Here is how to read one:

• Horizontal axis — Time of day (usually 24 hours)
• Vertical axis — Water height in feet above a reference point
• Peaks — High tides (the curve goes up)
• Valleys — Low tides (the curve goes down)

You can check tide predictions on our Weather and Tides page, which uses real-time data from NOAA for Southern California beaches.

Tides and Southern California

Southern California typically experiences mixed semidiurnal tides — that means we get two high tides and two low tides each day, but they are not equal. One high tide is usually higher than the other, and one low tide is lower.

The tidal range (difference between high and low) along our coast is moderate, usually between 3 and 7 feet. During king tides (the highest spring tides of the year), water can reach areas that are normally dry, giving us a preview of future sea level rise.

Try It Yourself

Next time you visit the beach:

1. Check the tide chart before you go
2. Note the time of low tide
3. Arrive about an hour before low tide for the best tide pooling
4. Watch how the water level changes over a few hours
5. Look for the "wrack line" — the line of seaweed and debris that marks the last high tide

Understanding tides connects you to one of nature's most reliable rhythms. The Moon pulls, the ocean responds, and life adapts. It has been happening for billions of years — and now you know why.