Tag Archives: Crew

Limiting Factors in Marathon Swimming – Part 2 – Environmental Factors

In Part One I covered the physiological limiting factors in marathon swimming.

The various environmental aspects of a swim are not insignificant. They are especially important in that they all lay outside the swimmer’s control and often even outside the control of the support crew.

Water Temperature


This is generally a known factor prior to a swim. Swims are either cool or cold water like the English and North Channels or warm water swims like Maui, Rottnest, Manhattan or Chloe Maccardels’ upcoming Cuba to Florida attempt. A few fall into an intermediate category defined more by the swimmer’s experience, such as the Catalina and Gibraltar Channels. Sudden changes in temperature are rare in marathon swimming and where they are possible they are also understood; such as South Africa’s west coast which is prone to sudden wide water temperature changes, and the California coast where the sudden transition from very deep water to a shallower continental shelf very close to the  mainland can cause cold water upwelling at the end of a marathon swim. Air temperature is obviously much more variable and a condition of the weather but extremes of air temperature are not usual during a swim. A five degree Celsius differential can be significant for a swimmer if such a drop is also accompanied with a breeze or wind which can sap the swimmer of body heat.


Lion's Mane jellyfish
Lion’s Mane jellyfish

The recent and future attempts at a distance and time records by necessity are held in warmer waters such as Cuba to Florida.  These water are home to jellyfish with debilitating stings such as Box Jellyfish. While the cold waters  of the North and English Channels are home to Lion’s Mane and Portuguese Man O’War’s endurance records are less likely and jellyfish stings in the English Channel are rarely more than intermittent, though the North Channel (the Mouth of Hell) can have miles of Lion’s Mane blooms, part of what makes it the ultimate channel swim. Attempts to swim in these waters divide swimmers in two ways: whether attempts should be made in locations not considered possible without additional protection or exceptions to the usual rules, and if so are jellyfish protection suits acceptable or the thin edge of a wedge that will inevitably lead to more overt (or hidden) performance enhancing suits? (See Evan’s analysis of his survey of marathon swimmers for an excellent overview of the contradictions of divisions and unity in the community).


The Man In The Grey Suit is a subject of great concern (and discussion) for distance swimmers. Not of any real concern here in the north-eastern Atlantic, they are a greater hazard in the warmer waters elsewhere, particularly California, the Caribbean, Hawaii, South Africa and Australia. The Cook Strait Channel swim in New Zealand is unique in having a shark evacuation rule. Shark cages have been used for marathon swims in the Caribbean and South Africa at least. Shark cages are however considered swim assistance as they increase the swimmer’s speed through eddy current drag. Other possible control methods include electronic shark repellents (whose effectiveness is not entirely assured or quantified), armed boat crew or armed or otherwise scuba diver outriders.


These are amongst  the most variable of environmental factors and therefore potentially also the most limiting. Because swimmers move slowly relative to even a sailing boat, we are vulnerable to slight deviations, miscalculations or just insufficient data, the most likely cause. Even in such a well-travelled and mapped location as the English Channel, especially for swimming, pilots will occasionally speak of tides arriving early or late or with a difference force than expected. Tidal currents are understood at a larger scale, hundred of years of navigation have mapped the seas for craft, not for swimmers. Tides act in a similar chaotic way to a weather system, which means that small deviations will always creep in. The only way to improve accuracy of prediction is to improve the data, and this is not practically possible or even desired for small tidal variations. As swims occur in less well-known or new locations, the likelihood of discovering unknown local variations outside marine charts increases. Half a knot current, barely detectable to a boat, is enough to deviate a swim over hours from a projected or necessary course.

Global tides
Global tides

Crew and boat

Any English Channel pilot will confirm that one of the most likely causes of unsuccessful Channel swims is poor selection of support crew. The most likely cause is mal-du-mer, seasickness. For some people seasickness is a completely debilitating ailment that can sap all willpower and strength and there is no way to know whom it will strike. The solution of course is to have experienced crew. Even this can fail because people experienced on powered craft will be at the mercy of the choppy water amplified on an almost stationary craft. Other crew issues can also arise, whether accidents or other illness. Anyone who hasn’t been on a rocking boat looking down on a swimmer is unlikely to understand! And not unknown are mechanical problems on the pilot-boat. Most pilots are by necessity practical mechanics able to address problems as they arise, but not all problems can be fixed with a wrench and hammer while rocking about on the sea.

Channel boat The Viking Princess
Channel boat The Viking Princess out of the water


Weather changes are the bane of English and North Channel swimmers particularly. Other Channels like Tsugaru and Gibraltar and Cook are also subject to constantly variable and unpredictable weather patterns. If you are used to the predictable weather of the west US coast, with morning offshore and afternoon onshore breezes, knowing your swim will almost certainly take place with a 48 window, the difficulty of allocating two weeks or even long (like the North Channel) and still being completely unsure of getting in the water is shocking. Weather constraints obviously ran the full gamut. In the North, English and Gibraltar channels the main concern is wind (and its effect on the seas). Fog can also be a problem with 2012’s Channel season infamously seeing three solos on one day abandoned within a kilometre of France for the first time in 137 years. I’ve warned previously that fog may be the most dangerous weather condition for swimmers. In warmer humid climes like Round Manhattan, and the Caribbean, lightning storms are a serious cause for worry, a swimmer or boat caught exposed out on the water is in real danger. Having to wait for or even postpone a swim is something many marathon swimmers have undergone and the mental pressure this brings is often not inconsiderable, which I will discuss further in the next and final part.

Coming in part three, Psychological Factors.


Back from Dover and a lot to write about when I get a chance.

It was…interesting, often in the Chinese way. Highs and lows, as always with Dover. More friends old and new (Marcel Degreef, Jane Murphy, the Israeli relay team, Caroline Chisholm, Paul Massey, Howard K., Bobo). Success and failure.

I’ve become increasingly convinced that a soap drama set with Varne would entertain the swimmers of the world. We wouldn’t even need a script, just the things that happen every week for the Channel season. I’ve suggested to David that Brad Pitt play him.

What are your suggestions for Evelyn? Plenty of you have been there.

It’s up to Gábor to write up his own story, I’ll be doing a version as some of you know about my other plan.

Anyway, the season still isn’t over, Alan is back to Dover this morning. He hasn’t decided about going public this time, so I won’t give any details for now. Caroline Chisholm is still hoping for a final slot after a loooong wait. Her last chance for this year is on the final unbookable tide in the third week of October. She’s also offered to crew for Alan Smith, so if you are following her blog or Twitter, she’s one of the good ones.

Now available to crew.. :-)

I know we have some people secretly booked for 2011 & 2012. I’d love to help more.

(Some might be surprised that I know who they are.

Overnight ferry tonight, home tomorrow. Free from seemingly endless real life cop pursuit shows the guys watched on the TV, interspersed with, I think, the same X-Factor episode repeated at least 3.

Met Jane Murphy, Freda, Paul M., Howard K. & fellow Channel twitterer Caroline Chisholm on the beach and had a good chat this morning. Caroline is now hoping to get out on the last unbookable tide.

Back in Dover

Well, I never thought I’d be back in Dover so soon.With some pressure from Eilis and Rob and the others, Gábor asked me to crew for him with Sylvain and his friends.We arrived yesterday.

The weather deteriorated from nice and warm at Heathrow to 9c by the time we reached Varne.Alan Smith and his crew were already here and an Israeli one-way relay who have been waiting for over a week. But Varne is unusually quiet.

Yesterday we had torrential rain and it was freezing cold in the afternoon.We didn’t even go for the first day swim even though we went down to Dover.

Gábor had been trying to get his pilot for a few days before finally making contact yesterday evening, to be told there is a good chance of swimming Wednesday morning.We’ll have confirmation this evening hopefully.

We met 2 members of the Irish Water Polo Relay Team out in the water. They swim tonight on Louise Jane and will have a Tracker.

We went to see Pace Arrow but she was away from the slipway.

Weather is much improved obviously today.Water was lovely and like beginners, Gábor and I each lost a left sandal to the rising tide.

Alan is third slot and unhappy with lack of communication from his pilot the last few days. But we are hopeful he will swim Wednesday or Thursday.