International Surfing Day

What the day is

International Surfing Day is observed on June 21, around the solstice. It was set up by an ocean conservation group alongside a surfing magazine, and the environmental half of that pairing has always been part of the point.

Origin and background

A wave is not moving water. It is energy moving through water, and the water itself mostly circles in place as the energy passes, which is why a floating gull rises and falls rather than being carried off toward the beach. What a surfer rides is the shape that energy makes.

That energy is usually old and from a long way off. Storms far out at sea transfer wind energy into the surface, and the resulting waves sort themselves out on the journey, because waves with a longer interval between crests travel faster than short ones. The long-period swell therefore outruns the rest and arrives first, sometimes days ahead of the weather that produced it, which is why a clean groundswell can turn up under a blue sky with no wind at all.

Breaking is a depth effect. In deep water the circular motion beneath a wave is unobstructed, but as the bottom shallows it interferes with those circles, slowing the base of the wave while the crest keeps its speed. The wave steepens until the top outruns the bottom and topples, which happens roughly where the water depth drops to a little over the wave's own height. A gently sloping sandy bottom produces a slow crumbling break; an abrupt reef makes the wave stand up and throw forward all at once.

The conservation element follows naturally, since surfers are among the first to notice when water quality fails, and beach closures after heavy rain are a recurring reminder of where runoff goes.

How to take part

• Take a lesson rather than borrowing a board and guessing.
• Learn to read a rip current before you need to.
• Check water quality reports after heavy rainfall.
• Join a beach cleanup, which is what the day was founded around.
• Watch a swell arrive and note that the weather never came with it.