The surf is a very powerful natural phenomenon. Many years ago the distant sound of breaking surf could sometimes even be heard on Tamborine Mountain. This is no longer possible, but from the Mountain we can still see evidence of the surf's power, when heavy surf throws plumes of salt spray high into the air along the coast.
Most ocean waves are caused by wind blowing over the surface of the ocean; friction between the air and the water transfers energy from the wind into the ocean and pushes the particles of water into a circular movement that creates the shape of a wave. Ocean waves appear to be movements of water, but they are really movements of energy, and although ocean waves can travel great distances, there is actually very little forward movement of the water particles themselves.
Waves organise themselves into sets, because energy is transferred from the leading and trailing waves to the central waves it is these waves that become the largest in the set.
Surf is a breaking wave and it is created when a wave makes contact with the seabed and friction slows the velocity of the wave base, but the top of the wave continues to move at the same speed. Eventually this speed difference causes the wave to tip forward, break apart and release its energy.
Breaking waves exist in a highly variable environment influenced by wind, tides and currents but it is basically the profile of the seabed which creates different types of breaking waves. These have been classified into different types based on changes to the wave surface profile during the breaking process.
Surging waves are found in deep water, they are stable and do not break.
Spilling waves are found where there is a sloping or gentle gradient of seabed; the crest of the wave crumbles at the top and spills down the front of the wave, dissipating energy uniformly.
Plunging or dumping waves occur where the seabed is steep or shallow, and the base of the wave is slowed abruptly, the crest of the wave curls forward and plunges over the front of the wave, releasing energy suddenly.
Rip currents occur when the mass of water released by the waves quickly returns seawards to maintain the water level. Recent studies of the morphodynamics of rip currents have shown that most rips follow a circulation pattern and that if a person is caught in a rip they are 4 times more likely to be recirculated to shallow water rather than being dragged offshore.
Many humans are permanently captivated by surfing and the exhilarating sensation of being lifted and carried by the dynamic power of the waves. We are not the only species to enjoy the surf; anyone who has had the thrill of sharing the waves with a surfing dolphin can sense their enjoyment as they demonstrate their superior surfing skills.