Surfing is enjoyed by millions of people. Surfing relies on the power of the wind to pull up the surface of the ocean into swell waves.
These swell waves are broad and shallow when out at sea. But the water on the move is not just the water you see above the surface. Just like the part you see of an iceberg is only a small part of the berg, so the swell wave you see on the move is only part of the wave. The rest is inside the sea.
Swell waves can cross oceans. But when they come to the coast the part of the wave in the sea has nowhere to go. It starts to scrape against the shore and this slows it down. Because it has nowhere to go except up, all the water in the wave begins to rear up. That is why waves near the coast are higher than those just a little way out to sea.
The wave is now very steep and is still moving forward. Eventually it becomes so steep that the crest starts to curl and break.
When the crest breaks it mixes in air bubbles with the water. This is called white water and the breaking wave with white water in it is called the surf zone.
Water is heavy. The energy in the wave is produced by the weight of water and the speed it is moving. Even small waves can knock you over or, in the case of surfing, carry you for a ride, so treat the waves in the surf zone with respect and avoid them in stormy weather.
A surfboard is a light, strong board. Surfboards were invented in Hawaii, and usually made from wood. These were very heavy, soaked up water and often sank.
Modern surfboards are made of polyurethane or polystyrene foam covered with layers of fibreglass or resin. These surfboards are much shorter, they will always float and are designed to go as fast as possible.
There are many kinds of board, but most have a keel, a fin on the back and sometimes additional fins along the sides.
There are two kinds of board: longboards are often over 2.5m round-nosed and broad, so they are more stable and easier to use. Shortboards are for experts. They are thinner and have a pointed nose. All are brightly painted.
