Tide and surf: why the same spot changes in three hours

A wave breaks when the water gets shallow

A wave stands up and breaks when the water under it gets shallow enough, roughly when the depth is a little more than the wave's height. The tide moves the water level up and down twice a day on most coasts, so it moves that point too.

• Too much water: the wave rolls over the reef or sandbar without standing up, or breaks soft and late.
• Too little water: the wave stands up all at once and dumps, or breaks onto shallow reef.

Each break has a tide it likes. Many reefs need mid to high tide to cover the rock. Many beaches work best on low to mid tide, and some only on a rising tide.

Try it

Banzai Pipeline likes low to mid tide. Malibu First Point likes mid to high tide. Move the tide and watch one get better while the other gets worse. The numbers come from the same tide check the BarrelFare score uses.

Where you see it on BarrelFare

Each spot page says which tide that break likes, and the forecast scores every hour against it. A good swell on the wrong tide scores lower, so the best hour is often when the swell and the right tide meet.

How to read a surf report and forecast