Weatherproof your swimming: Understanding Swell

Simon Murie from Swimtrek shares expert experience on how to adjust your swim stroke for swell

Blake Wisz

‘Swell’ is the term used to describe a series of mechanical waves found in the sea or lakes set up by distant weather systems.  While chop is generated by local winds, the size of swell is coming from far away.

Swimmers most often encounter swell in the sea. While sea swimming can be an enlivening way to experience the wilderness of our waters, big swell, when the surface of the water is turned into a series of peaks and troughs, has an undeniable effect on the way you propel yourself through the water.

With some adjustments, swimming through big waves or swell can be thrilling. Simon Murie from SwimTrek shares his advice for these conditions with us.

Getting started

When planning an open water swim in swell, bear in mind:

  • Your ability to cover a set distance is reduced due to harder conditions
  • Your visibility in the water to other traffic and other swimmers is significantly reduced (you can lose sight of your swim buddies unless you stay close). Counteract this by making sure you are as visible as possible by wearing a bright swim cap and perhaps taking a tow float.
  • Sighting and breathing will be more difficult. Having the skill of being a bi lateral breather who can opt to breathe to one side is handy in this situation; if the swell is coming from your right, then try and breathe exclusively to your left. Try timing your breaths to the crest of the wave rather than the trough.
James McGill

Weather forecasts and choosing a location

Check weather and swell forecasts, looking especially for wind strength and direction. White caps on waves will typically start around Beaufort 4 (13-18MPH). A direct on-shore wind will generally cause a rougher water state than an off-shore wind. 

There will be times when the water may be too rough – everyone has different conditions that they feel safe in, so listen to your instincts.

Choose your swim spot with the conditions in mind. If your location is facing right into the swell, see if you can find a spot that faces a different direction, offering greater protection. For example, on a small island you can always go from the lee (protected) side of the island.

Entry and exit in swell

A key issue that swimmers often overlook is getting out safely. Whether you exit on a beach or onto a boat, this can be the trickiest part of a swim. If you don’t feel comfortable in the conditions, or in getting out, save your swim for another day. Preparation wise, nothing beats experience in the conditions. The more exposure you give yourself, the more confident you will feel.

Look for an entry spot which avoids any objects, natural or manmade, such as rocks, groynes or piers. Avoid any places with rip currents or locations that have heavy boating traffic or are near boating lanes.

Two dangers are: waves ‘dumping’ on the shore, which can make it hard to get your feet down and walk out without being hurt (if the beach is pebbly dumping waves are particularly dangerous); and shelved beaches where there is a huge suck back by the retreating tide – making it hard to get out of the path of the next breaking waves and onto dry land. Be aware that the shape and force of waves and suck back can alter dramatically as the tide comes in and out within the course of a swim – it is always worth talking to locals.

Top Tips:

  • Check exit conditions before getting in – they are likely to be made harder by swell.
  • Swimming at low tide can also often mean the waves are more manageable.
Josh Withers

Changing your swim stroke

  • Swimming into swell or chop: you will benefit from a shorter, flatter, punchier stroke.
  • Swimming with swell behind: exaggerate the glide more to benefit from the push of the waves. 
  • In rough conditions: widen your stroke entry to give you more stability. 
  • Sighting: attempt to sight on the crest of a wave rather than the trough and sight on bigger landmarks that are easier to see. If this is still difficult, then sighting by the sun can be effective; when looking at your target, if the sun is to your left at a 9 o’clock position, then keep the sun at this position throughout your swim.

Group swims in swell

Swimming in a group is good for safety and motivation. One trick when swimming in a group is to keep those swimmers who breathe to the left on the right side of the group and vice versa. This ensures that all swimmers can keep an eye on the rest of the group, reducing the risk of separation. Ideally, never swim alone, but if you do, explain your swimming plan to the lifeguard or let someone know your plans (where and how long you expect to be in the water) and arrange to call them when you finish.

Be aware that it can be hard to see each other in swell – not only can the water quickly move you apart from other swimmers, the troughs and peaks can hide you from each other. Talk about this before you get in and make a plan.

Torsten Dederichs

Ultimately, the sea is an awe-inspiring body, and one in which we are privileged to swim. With the right considerations, swimming through mountainous oceans can be exhilarating – an embodiment of the changeable face of nature, which makes our swimming so truly wild.

Many thanks to Simon Murie at SwimTrek for his excellent practical advice.


Bonnie Radcliffe