If you go sea kayaking anywhere outside a harbour, waves are present the whole time. When you launch from a beach, usually you launch through small waves.
And they always look a lot bigger when you're sitting in a kayak than they do from anywhere else.

n water less than 4 or 5 metres deep, there will always be the occasional wave which is larger than the rest and which will unexpectedly peak and break. An experienced kayaker knows where and when to relax because there's nothing to worry about.

An experienced kayaker, and particularly one who is addicted to exploring the coast from up close, also knows when to keep looking over his or her shoulder.

Waves at sea
Nearly all waves are created by wind blowing over water, and they travel in about the same direction as the wind which created them. The wind needs both time and distance to create large waves. The area over which it blows while doing so is technically known as the fetch.

Local winds. After a day of Force 5 winds there will be quite large waves downwind of any open water more than a kilometre or so wide. Waves directly created by local winds are steep and a short distance apart (short wavelength). If the wind changes they soon fade out and cancel each other out.

If you are in a fast sea kayak and you want to travel in the same direction as wind-generated waves, you can make your trip more fun and possibly faster. Wait until the back of your kayak sinks down and it feels as if you are paddling in treacle. Take a few hard forward paddle strokes to accelerate and you will be surfing on the next wave.

Swell was created by mid-ocean winds blowing consistently in the same direction for a long period. Even a fast sea kayak is seldom able to catch and surf swell out at sea. Its slope is too shallow and it travels too fast, often at over 20 knots. It has a very long wavelength which enables it to travel hundreds of kilometres outside the fetch.

Out at sea there is usually some swell. It is defined by the IHO Hydrographic Dictionary as "ocean waves which have travelled out of their generating area. Swell characteristically exhibits a more regular and longer period and has flatter crests than waves within their fetch". It consists of parallel lines of waves, all travelling in the same direction and seldom more than 2 metres high in sea kayaking waters, but with a distance between crests (the wavelength) that may be 30 metres or more. A really big swell may not be very high but its wavelength of hundreds of metres will give you a hint of vertigo and a proper feeling of your own insignificance as each wave passes beneath you.

Swell consists of energy moving though the water. As each green wave goes past you, the surface of the water goes up and down but the water itself does not go anywhere. Swell on its own is no problem at all for sea kayakers. In calm conditions it does not create any foam or turbulence on the surface. Unless it encounters a strong wind or current going the other way, it does not steepen and break in deep water.

When it reaches shallow water it will create breaking waves. The longer the wavelength, the faster it travels and the more it will rear up on entering shallow water. However you will still be able to find sheltered water without waves in a harbour, an estuary or under the lee of a headland.

Groundswell. To some experts this is just another word for swell, to others it means swell that is starting to touch bottom. According to the IHO Hydrographic Dictionary it is "a long high ocean swell; also, this swell as it rises to prominent height in shallow water". Either way, the waves are not breaking.

Breakers. When a wave enters shallow water, slows down and starts to break, it turns from moving energy into moving water as tonnes of water cascade towards the beach. The way a wave breaks on a beach is of direct interest to kayakers. See The Nature Of Surf - Spilling Or Plunging.

When might you encounter a breaking wave somewhere other than next to the shore? In windy conditions the crest of a wave may break even in deep water, spilling forwards but with no great force. Waves with breaking crests (whitecaps or white horses) are common at sea in winds of Force 4 and above.

Usually you can easily deal with them with a quick low brace support stroke. In worryingly windy conditions, Force 5 or above, you may occasionally be hit by the spilling crest of a wave one metre high. This may look intimidating but it is still only the crest which is breaking. It has little force and you can easily cope with it using a high brace. If waves are much higher than that, you may capsize unless you are an experienced kayak surfer. Hold your breath and wait a few seconds until things are calmer, then roll up. Sea kayakers don't generally venture out in conditions that windy.

It is difficult to tell, looking down at the open sea from a cliff top, whether there is a big swell running. If you go and stand by the water's edge at a nearby surf beach you will get a better idea of the size of the swell.

Boomers. A very useful American word for isolated, big, breaking waves. If there is a big swell running, to avoid unpleasant surprises you should stay clear of isolated shallow areas in the sea. That means reefs, offshore banks of sand or mud, and the sand-bars which often exist at the mouth of a river. A reef or sand-bar one metre below the surface is likely to make every wave peak up and break. If it is two metres below the surface, only larger waves will break.

On a coast which is exposed to ocean swell there may be the occasional big, isolated breaking wave over a reef covered by 3 or 4 metres of water. Most waves will just roll smoothly over it but extra-large waves may break there once every 30 or 40 minutes. However engrossed you are with the person in the next kayak, your GPS or those strange birds on the cliff, always keep an eye on the next two kilometres of your course in case of a flash of white. On unfamiliar parts of exposed coasts, check the chart for shallow areas and stay clear. Your editor broke that rule early in his sea kayaking career and was lucky to get away with it. See How Not To Do It.

Wind-against-tide conditions
If the wind blows in the opposite direction to a current it will create steep waves, close together, known as "wind against tide" or "wind over tide" conditions.

Generally the waves are small and just give you the choice whether to paddle with the tide or against it. If you choose to go up-tide each wave will push you on your way a little and you may be able to surf on some of them. A current of 1.5 or 2 knots opposed by a Force 3 wind may create a noticeable chop, with steep waves close together, which will be worrying for the beginner but fun for everybody else.

Wind over tide conditions are seldom a problem, even in parts of the world with a very large tidal range and therefore strong tidal streams. Wind over tide conditions are significant where local currents are strong. They can come as a real surprise where there are reversing currents, as in a narrow channel or estuary where the current quickly makes a 180 degree change of direction every six hours. When the tide turns and suddenly opposes the wind and waves, things can get rough. For example, a windy day in the Menai Straits. The straits separate Anglesey from the mainland of Wales and look like a wide river running through a canyon. Tidal streams here are the third fastest in Britain, often flowing faster than walking pace and sometimes reaching 8 knots. The walls of the canyon funnel the wind. When the tide turns, the Straits can suddenly get very choppy and cause real problems for novice kayakers.

Swell-against-current conditions
When waves encounter a current flowing in the opposite direction they get steeper, taller and closer together. This is very similar to what happens when a wave encounters shallow water.

Charts and pilot guides warn of a few places round Britain where large waves regularly march in from the ocean and meet unusually powerful currents going the other way. At Sumburgh Head in the Shetland Islands, this combination creates a clearly-defined area of rough sea in winds coming from any direction except the north east. At maximum flow on spring tides, the pilot book says there is a "confused, tumbling and bursting sea" in which "vessels often become entirely unmanageable and sometimes founder".

In France, the Gulf of Morbihan is a large area of water with only a small opening to the sea, and a large tidal range. Tidal streams in the entrance to the Gulf often reach 9 knots. This is very, very fast. That sort of speed is normally associated with dangerous conditions like those we describe here. Powerful swirling eddies in the entrance can be disconcerting and occasionally send a yacht in a 360 degree turn. However local kayakers tell us there is nothing dangerous about the Gulf unless the outgoing tide is opposed by a swell coming in from the south-east / south-west. That combination can create a raz in the entrance.