How surf actually works
Seven short pieces on the parts of a forecast that mislead people — why a wave breaks where it does, what separates a wall from a crumble, which high tide you actually want, and what the water is doing while you sit on it.
Every figure here is solved, not drawn. The wave fields come from the same model that runs the forecast, on real measured seafloor. The numbers are computed from the inputs printed next to them, so you can check the arithmetic rather than take our word for it — and where the science genuinely does not know the answer, the page says so.
Start here
What a wave is doing, and why it falls over where it does.
- What actually makes a wave break
A swell crosses an ocean intact, then falls over in under a second. Here's what changes.
Answers: “Why does a wave break where it does?” · 6 min
- Why period matters more than height
A 2 ft groundswell can out-break a 3 ft windswell. Here's the arithmetic.
Answers: “Should I care more about the height or the period?” · 5 min
The four levers
Swell, seafloor, tide and wind — what each one actually controls.
- What makes a wave powerful, and what makes it mushy
Same height on the forecast, and one of them is a wall while the other is soup.
Answers: “Why is it three foot and completely gutless?” · 8 min
- How the tide moves the break
Same swell, same bank, two tides, and a different wave.
Answers: “Why is my spot good at one tide and useless three hours later?” · 5 min
- How tides actually work
There are two high tides today and they are not the same height. That difference is your session.
Answers: “Which high tide? And why is it always later than yesterday?” · 6 min
- Why two breaks a mile apart get different waves
One swell arrives. The ground underneath decides what you get.
Answers: “Why is it four foot at one spot and flat a mile away?” · 5 min
The water itself
Currents: what moves you down the beach, and what pulls you out.
- Why the water pulls you sideways
You paddle out at the stairs and come in four blocks north. Here's what moved you.
Answers: “Why is the current so strong today, and where is it taking me?” · 8 min
Now go and read your own break
Everything on these pages is applied to 111 California breaks — each one solved on its own measured seafloor, at each hour's real water level.
Open the live map