This is not medical advice, just some of my musings. It is not 100 exhaustive but may be useful.

Medical things to be aware of whilst preparing / training / for medical sign off.

Declare anything of relevance to the person signing your medical and in self declaration for event.

In particular, in line with the American Heart Association’s 12 point guidance for screening:

Any Family, or personal, history of premature cardiac disease (less than 50 years) or sudden death in adulthood (including Swimming Induced Pulmonary Oedema – SIPE)

Excessive cough, chest pain or breathlessness exertion (especially during training) which is out of keeping with the effort involved.

Any respiratory problems including asthma / COPD.

Any medications including analgesia, inhalers etc. (these should also be declared to the organisers / support team and kept close at hand if required.

Any allergies – including foods / poisons / anaphylaxis – have antihistamine and epipen with your support team if required and highlight potential issues early.


Not medical advice – just some things to think about - Hypothermia

(Photo at Parliament Hill Lido – credit N.Murch)

Definition: Core temperature below 35 degrees Celsius (usually above 37 degrees)

Cold water takes heat way much faster than cold air, but the combination of the two can potentially be fatal. Minimise risk by being prepared: acclimatisation and gradual supervised adaptation, multiple layers of clothing for post swim, swim / woolly hat, earplugs. Avoid alcohol before

The “umbles”

From best to worst state:

32 to 35 degrees

Grumbles: negative outlook, may be shivering

28 to 32 degrees

Fumbles: fine motor movement, should be shivering

Mumbles: slurring of words, should be shivering

Stumbles: inability to walk unaided, should be shivering

Below 28

Crumbles: below 28 degrees Celsius, body cannot shiver, may lose consciousness as drop blood pressure and heart problems may occur – Medical emergency

After drop – core temperature is lowest approx. 6 minutes after come out of cold water – need to plan for this drop

First aid Management of hypothermia:

Move indoors if can, or at least get out of the wind.

Remove wet clothing and get dry

Passively reheat with multiple layers of clothing/ blankets, especially feet with socks and head with hat. Also lie on material where possible – i.e. off cold ground.

Get people to lie next to them but not to massage them. Do not use car heating or hot shower etc. – may cause collapse due to low blood pressure as blood diverted to skin too quickly.

Warm non-alcoholic drinks consider further medical attention if required.

Envenomation Jellyfish

Not medical advice – just some things to think about - Jellyfish

3 potential effects:

Immediate allergic – allergic type effect
Immediate toxic – response to toxins
Delayed allergic – may flare (again) approx. 10 days later (2 weeks later, photo credit Richard Parker) – this may scar!

Not medical advice – just some things to think about - scar

Treatment is to remove residual stinging cells with weak acid liquid e.g. vinegar and put in water as warm as can tolerate to deactivate the poison.

Aftercare: local wound care as may her secondary infection, antihistamines for itch and inflammation (personally take before swim to minimise risk of reaction during swim, may sedate therefore take the less sedating ones and try before swims). Consider steroids if severe reaction.

In big swims – just keep swimming if can!

Weever fish

Barbed fish that stings when stood upon. Severe pain followed by foot swelling. Treatment is to put foot in water as warm as can tolerate to deactivate the poison (at least 40 degrees Celsius)

Blue-green algae

These are in fact bacteria, not algae, and use their pigmentation to make energy in the same way as plants. They can be found in any body of water which is slow-moving. They often floats as blooms when numerous. They may produce toxins that make swimming dangerous if swallowed or even by touching the skin. They may cause rashes, vomiting, fever, headaches and even organ failure. Avoid swimming if warned against it or if the water appears discoloured. If someone has been exposed then shower them immediately, if unwell they should seek medical advice.

Weil’s disease – Leptospirosis

This is a bacterium that can be contacted from rodent or farmyard animal urine. It presents non-specifically with flu-like illness, conjunctivitis or abdominal pain. This can progress to jaundice, kidney failure, meningitis and excessive bleeding. It is a medical emergency and if unwell tell the medical staff you swim in open water. It has a delay of onset of 7 to 12 days after exposure. Present yourself early if concerned.

“Duck lice” / “Swimmers itch” 

These are small parasites that cause local immune reactions and severe itching when ‘bitten’. They actually originate from snails that live in slow-moving water, particularly when very reedy. They are relatively harmless in the UK, but can cause intense itching that can last 24 hours. Local treatment with camomile or Epsom salts may help. Certain antihistamines may help too.


Need to ensure passing adequate urine – at least every 2 hours. I personally feel that fluid intake should be at approximate double that of a 24 hour requirement for maintenance as there are insensible losses (ie. on breath / sweat etc.).

Recommendation is 25 to 30 mls / kg /24 hours. So 100kg man should have 2.5L to 3L in a day, so approx. that amount for a 12 hour swim. However train on this – excessive pre-hydration may increase risk of SIPE.

Pure water may cause problems too though, as salt (sodium) is also lost in sweat and replacement with pure water may cause a dilution of the blood which can cause problems with both physical performance and health. I personally do not subscribe to the argument that being in salt water will replace salt lost in sweat so I take an electrolyte supplement containing Potassium, chloride and magnesium (amongst others) to optimise muscle and brain function. Try this in training if going to use – often effervescent so make up day before if needed so can become ‘flat’. There are some basic electrolytes in some of the branded carbohydrate drinks so read the label!

Swimmers ‘rots’

Loose stools may be an issue with open water swimming. I personally feel it is rarely due to gastroenteritis or ‘dirty’ water:

Most people use a carbohydrate gel or solution to feed whilst swimming long distances. These are usually composed of small molecules that provide rapid release energy but can cause the stomach to distend (causing nausea) and may have, in my opinion, laxative effects. Many distance athletes get “runners’ trots” (think a certain female marathon runner) and this may be due to excessive pure water consumption, the laxative effect of feeding agents and diversion of blood away from the bowels to the muscles. It is not dirty water that (usually) causes swimmers to develop gastrointestinal upset.

Gastroenteritis can be cause by multiple bugs, but the most common causes are probably E.Coli or crytosporidium. Most illnesses are self-limiting but if severe or persistent then seek urgent medical attention.

Otitis externa (or Swimmers’ Ear)

This a common infection of the outer ear if kept moist or have small blemishes or cuts in the ear canal itself. Ear plugs may help avoid this (as well as keep you warm). Eardrops may be required to help clear it.


See my blog on nutrition…


Is one of the most common reasons a swim gets aborted and is due to an imbalance in what is perceived by the eyes, ears and brain. Also delayed gastric emptying may play a part. Eating a full meal immediately before swimming or crewing is clearly a bad move as will slow gastric emptying, as will energy drinks especially those with small sugar molecules and fat too.

Non pharmaceutical methods: stay in middle of boat and as low as possible to minimise the sway, also fix on a relatively immovable object such as the horizon. Foods such as ginger may help, as may wrist bands. The evidence for these is limited but anecdotes suggest may work for some people.

The commonest prescribed medications include Cinnarizine (an antihistamine that blocks signals from the ears but may cause drowsiness) and patched containing Hyoscine (Scopolamine, US) that may also cause secretions to dry up… Practice beforehand before taking on the day of a big swim.

Cardiac Problems

Those at risk may develop cardiac problems. Excessive exertion may cause heart attacks or funny heart rhythms (arrhythmias) which may cause cardiac arrest. These are uncommon but should be observed for.

Swimming induced pulmonary oedema (SIPE) is fluid in the lungs. It is reported in 1 to 2 percent of open water swimmers and has up to 40 percent recurrence rate. It appears relatively similar to altitude induced pulmonary oedema found in mountain climbers.

Risk factors include breathlessness out of keeping with perceived effort in training. High blood pressure and over rehydration before and during swim.

Possible mechanisms include a ‘Perfect storm’ of aspirating small amounts of fluid, cold water or a wetsuit / cold water causing water to pool in core, lying flat for many hours, increased blood flow to lungs (up to 20 times) but lymphatic drainage which removes it being only ten times and Capillary leak in lungs due to exertion.

Things to watch out for are a drop stroke rate, confusion / disorientation, cough and then frothy or pinkish sputum from nose or mouth (think race horses) and a bubbly sounding chest. It has rapid onset and relatively rapid resolution. This condition may be during the swim but may be delayed until up to 24 hours after completion of the swim, I would recommend monitor stroke rate while swimming and level of orientation at feeds.

Management includes removal from water’ Sit upright. Keep awake, oxygen if available, and cardiac defibrillator to monitor if chest pain or tightness.


Keep inhaler(s) close to you at all times, most can be accommodated in a costume or at least with beach crew. If more wheezy don’t swim. If wheezy after then use inhaler and reassess.

Sleep deprivation.

Learn to swim tired!


Mostly due to water and electrolyte deficiency as well as cold… see above. Learn to stretch in the water.

Musculoskeletal injuries

Shoulder injuries are often psychological – there, I said it. Does the pain persist after or has it disappeared immediately post swim? Shoulder problems may range from impingement of soft tissues to rotator cuff tendinitis or tears. Avoid injuries in training, but on the day of a big swim, is it worth persisting in pursuit of glory?

Analgesia is slightly controversial – dispersible paracetamol is, in my opinion, ok. Mix in feed and take with feeds at prescribed times and doses. NSAIDs including ibuprofen, may cause indigestion (lying flat and ’empty stomach too) and kidney problems especially if dehydrated and muscle break down mid swim. Advise to avoid if possible. Long term use may increase risk of stomach ulcers as well as cardiac problems. Acutely, after a swim, are probably ok. Naproxen is possibly the safest of this group of medicines.


Wear at least factor 50 sun cream even if cloudy – preferably one that is highly water-resistant and that has been tried in training – if some gets in your eyes it can be painful so try different ones. Consider a knee-length costume if allowed to protect back of legs.

Nick Murch – Take home message: Train as you mean to fight but stay safe!