I haven’t previously tackled the subject of water exits specifically, though I have covered it in general terms in a number of articles. Especially those articles which try to condense the basics of open water swimming considerations for beginners and irregular swimmers, such as beginners or triathletes
I haven’t written about exits because anyone with even moderate open water experience knows that exiting rough water safety is one of the main challenges of open water, and often the best and only solution is to not get in. But it’s a recurring question and as such I need to address it, and it seemed like a challenge to write about. I considered entitling this article How To Safely Exit Rough Water, but there is no way to guarantee safety with any aspect of open water swimming, and especially not with Exits. The best you can and should do is to grow your experience and learn more about the water, the coast and your own capabilities. And honestly I wasn’t sure how much there would be to write. Turned out as I starting writing… more than expected.
So, if I’m finally going to address the subject, you know I’m going to do so in detail and try to go into the esoteric areas if possible. So once again, something that started out as a simple short article, gets turned into a two-part detailed exploration.
There is a little science in this, (but no numbers), which you can skip, but you might find useful in understanding more about water motion near objects, and how that is relevant to swimmers. I bemoan the lack of genuine understanding about the sea and its wide range of behaviours and challenges amongst the large majority of open water swimmers.
With the exception with mega-lakes like the American Great Lakes, most fresh water bodies or rivers do not exhibit quite the same range of difficulties as the ocean coast, from lesser fetch, the distance over which wind can blow to cause rough water, to the lack of barnacles. However current in rivers presents similar difficulties to moving waves and can be treated similarly for the sake of this subject.
We need to begin with some safety statements:
- You should not be getting into open water before you know where or if you can safely exit.
- You should not let others decide for you if exit conditions are safe.
- Alternatively you should not get into the water simply because someone else is already in there.
- A corollary of these statements is that you should not be getting in the water in anticipation that a safe exit will somehow present itself once you have entered the water.
The 2015 Christmas Day swim story I featured of Sam Krohn’s rescue of a careless swimmer would not have been required if, issues of alcohol aside, the two casuals had known and applied the above rules, or a modicum of common sense. I have mentioned before that on occasion, for example that Christmas Day, people with little skill and no knowledge got in the water simply because they see me in there, and some have tried to say that maybe I shouldn’t be setting such an example. It’s an idea I reject, as I spent the time to build up my knowledge and develop my skill. The solution is not for more experienced swimmers to stop, but for us to encourage and educate others to improve their skills.
The ease of getting into the water in rough conditions bears no relevance to the difficulty and danger involved in exiting the same conditions. Injuries caused by exits are the most common injury in open water swimming, (basing this observation entirely on what I’ve witnessed over the years).
What is rough water?
Definitions of rough water vary somewhat by experience and swimming background but there are a few simple rules of thumb. I’ll keep it brief just a way of setting the context which we will later enter, so to speak, in talking about exits. If you want to read about swimming in rough water, go here.
Rough water occurs in cross-shore or on-shore winds. Cross shore winds blow as they sound, along the shore. On-shore winds blow from sea to land.
In many locations breezes will be offshore in the morning and evening but will be onshore during the warmest part of the day as air pressure over the water increases and the air flows “down” into the low pressure area over land.
With on-shores the wind can push up a choppy surface after blowing over only a couple of kilometres locally. (The distance of water over which wind blows is called the fetch). Depending on the local shore geography that can also happen by blowing along a shore if there are no headlands to interfere. Rough might include but is not exclusively waves.
Wind against tide (or sea) is another condition that can cause chop as the two opposing flow directions interfere with each other.
Chop is different to waves. Waves travel over distance and can tiny to very large, and can have short to long intervals between them. Large waves without wind or with off-shore wind are powerful and can be dangerous when exiting. Large waves with a short interval and with onshore winds are the most difficult situation. Chop is small wavelets with no discernible pattern that occur all over the water surface with great frequency.
Choppy water can be agreed by most swimmers to begin to occur in a Force Three onshore wind, (which is actually only a gentle breeze), with only a very short fetch. In a force three, you will see small whitecaps breaking fairly consistently.
The roughest water conditions are combination of chop, waves and wind.
Inertia and Flows – The Vaguely Science Section
Moving water is an incredibly complex system, and I am far from a theoretical fluid theoretician. Though I quite like the idea that I’m a practical fluid dynamicist, which in my case is just an overblown way of saying open water swimmer.
The inertia that moving water imparts to a floating or standing swimmer, coupled with turbulent and laminar flows and the opposing flows in waves, and with sudden changes in surface height due to amplitude changes, all combine to easily knock swimmers from their feet, sweep them past an exit point, push or pull them across a rock or off a stairs or ladder. What that means is rough water knocks you down.
Like a dog catching a frisbee in mid-air isn’t consciously applying Newton’s Laws of Motion, a swimmer exiting rough water isn’t thinking about laminar or turbulent flows or Reynold’s numbers, though in both cases what is actually happening can still be somewhat explained in those terms.
In the way that some people think open water swimming is easy because middle-aged men like myself wear Speedoes and frighten kids on holidays so it really can’t be a tough sport, similarly they think that because water is fluid and easily diverted, it can’t really exert much power on them.
One only needs to spend a few minutes playing in waist-high waves on a beach to gain some appreciation that waves, i.e. moving volumes of water possess significant inertia. But swimmers forget about the density and inertia of water and instead usually mistakenly focus on its fluidity and particularly the notion that the water will simply flow around them.
Water is slightly more dense than a human. That’s why we float. Water is actually the substance against which we measure the density of all other physical objects. It doesn’t compress well and it’s heavy.
Any moving body of water will possess significant inertia. Inertia is the physical tendency of something to keep moving or stay in place, unless acted upon by an opposing force. So even the aforementioned waist-high wave has the mass and inertia of not just the water beside you, but the entire volume of the wave behind. Moving water is amongst the most powerful and destructive forces of nature, even in small amounts. If you consider the damage potential of a small leak in your home significant, then don’t ignore the power of a waist-high wave.
How strong is moving water? A grown man is knocked over by ankle-deep water moving at 6.7 miles an hour.
That’s a fast flow, more like a rushing river than stormy conditions, you might think. Tidal current in the English Channel is up to 7 knots per hour. That’s over 10% faster. But think of it this way; if you halve the speed to 3.5 miles per hour, then you only need to be submerged up to your calves to be knocked over.
Water is turbulent near the ladder or stair at which you want to exit. Different types of flows will means there are slow or even non-moving layers of water adjacent to fixed objects like pier walls, The closer to a fixed object the less movement in the flow layer. Such flows can act on you and instead being pushed directly against a fixed regular object like a pier wall or boat, you will likely shear or be pushed with some degree of lateral motion, i.e. to the side. Turbulent flows are as they sound, irregular and unpredictable. Allied to this we add even more complexity, in that waves act in opposing directions, with the crest moving forward while the trough or base moves in the opposing direction, though this is further complicated (yeah, more complication) by the shape and speed of the wave.
I’m not thinking of all this when I’m getting out of rough water at the Guillameme at mid tide, but I am vaguely aware of it in a practical sense, in the same way that dog mentioned above runs and jumps and catches the frisbee. When as we know, dogs are actually likely to mix up Newton’s Second and Third Laws of Motion in a closed-book exam and are well-known to be rather poor at integral calculus.
I am though consequently aware that every exit needs care and attention and this section was intended to impart some of the reasons why. In the next section we’ll look at specifics, the features and hazards of different types of exit.
HOW TO: Tides for Swimmers, part 1 – Theory. It’s important that swimmers understand tidal aspects fully, especially those who live in high tidal range areas like Western Europe.
HOW TO: Tides For Swimmers, Part 2 – Local Effects. When considering tides, theory and local effects are often very different.
HOW TO: Understanding Waves, for Swimmers, Part 1. Waves, i.e. breakers are a difficulty for triathletes and new swimmers. Also important for coastal safety.
HOW TO: Understanding Rough Water: Force Three. Specifics of a marginal sea condition.
HOW TO understand Sea Area Forecasts / Shipping News. Weather forecasting is a useful skill for distance swimmers.
HOW TO: Beaufort Wind Scale – An essential observational skill for the OW Swimmer. Being able to read wind conditions is essential to understanding the sea and safety.