Happy reading, and don't forget to scroll down to the bottom of the page for photos sent in by other swimmers and support crew on how they have managed their own swims. Have suggestions, photos or videos from your own experiences you'd like to share here to help this resource grow and evolve? Let's chat, send me an email! wildbigswim@gmail.com

IMPORTANT: The information provided in this section has been developed with the support of persons working in the medical profession but it does NOT constitute medical guidance, so use it as things for consideration in your own preparations only.

13.1 A swimmer's basic physical needs during the swim

The swimmer needs, at very least...

Feeds: the swimmer needs a combination of fuel, electrolytes, and liquids for good energy and hydration
Urination: the swimmer needs to be urinating regularly in order to void the bladder and keep the kidneys working well
Cognitive alertness: the swimmer needs to be alert and able to verbally communicate their needs or issues
Ability to make forward progress: weather conditions aside, the swimmer needs to be able to make forward progress

If things do start to go sideways, here are things you might observe about the swimmer:

The swimmer's pace and/or stroke rate slow down, this may be a gradual or sudden decline
The swimmer's stroke rate stays the same but they are losing power to their stroke and their pace declines
The swimmer stops swimming intermittently in between feed stops, seemingly without a specific need or reason
The swimmer's speech is confused, they may not be able to think or express themselves clearly anymore
The swimmer experiences fatigue, cramps, dizziness, vomiting, changes to urine output, irritability

Some of the above observations, such as slowed stroke rate and irritability, might be perfectly normal because the swimmer is understandably tired, but it's important that the crew and swimmer are actively monitoring and addressing anything that signals a possible safety concern or issue.

13.2 Monitoring feed intake

The swimmer needs fuel, electrolytes and fluids to keep swimming, and the crew monitors their intake over the swim to make sure they're getting enough of each to be swimming safely. Feeding plays a huge part in whether the swimmer gets to the finish or not, and whether they'll experience other problems along the way. It helps to know a little about how digestion works...

The difficulty with the digestive process is that you can't sit down with pen and paper and try to map out specific times for how quickly foods will give the swimmer usable energy, it depends on a lot of factors, like what and how much is already in their stomach, their metabolism, overall fitness, rate of exertion, stress levels, etc. But it helps to know that liquids and soft semi-solid feed sources will be emptied from the stomach and processed into usable energy in the small intestine faster than solid foods. This is why most swimmers use a liquid feed as their primary fuel source, it also just goes down faster. So if the swimmer is having a hard time consuming their feeds, consider that liquid or soft semi-solid alternatives are likely to give them energy fastest.

During preparations for the swim, the crew need to know the swimmer's ideal intake per feed - how much calories, carbs, electrolytes, and fluids are they planning to take in. If the swimmer or crew are producing a written swim plan, make sure these details are clearly laid out so that the crew can understand them. Write them out per single feed and per hour, if that's helpful. If the swimmer deviates from the written plan as they are putting together their feeds in preparation for the swim, don't be afraid to ask why and even challenge if it makes sense, so that you understand the possible implications. A well-rehearsed feed plan shouldn't be changed at the last minute, unless those changes are things the swimmer has also practiced at some point.

The swimmer should have tested their feed plan in the months leading up to the swim. Some swimmers have cast iron stomachs and can eat cookies and juice for as their fuel source with no issues at all (you know who you are, much love your way!), while many of us have a harder time and need to find fuel products we can consume consistently and keep down. Testing the feed plan isn't just about whether it's palatable and will stay put, it's about whether it's safe too. The swimmer needs fuel, electrolytes, fluids on a regular basis, and in a balance that keeps them healthy enough to stay in the water. Unless the swimmer never ever had issues with feeds, they should also have other backup options with them in case their feeds aren't going down or staying down. The crew should know what these options are, when they might need to use them, and how they are delivered. See Section 7.4 Assume the feed plan goes to shit of this crew guide.

Here's what might happen with feeds:

The swimmer gets sick of them, the flavour, the smell, the thought of consuming them
The swimmer takes longer or stops being able to consume them, either taking in less than they should or none at all
The swimmer may ask for other things instead, which may not be of equal value (water, tea, treats)
The swimmer may vomit up what's in their stomach

What might be happening to the swimmer's body:

Energy: glycogen stores in liver and muscles deplete, they hit a wall or "bonk"
Dehydration: inadequate fluid intake can strain and possibly damage the kidneys
Heat stress: extreme temperatures can lead to dehydration and electrolyte imbalances (same impact to kidneys)

Hyponatremia: abnormally low level of sodium in the blood, often due to over-hydration (same impact to kidneys)

Things for the crew to consider:

Fuel: would the swimmer take the other backup foods? baby food pouches, mashed potatoes, sports gels?
Electrolytes: would the swimmer take plain water + unflavoured electrolyte drops or salt tabs?
Fluids: plain water or tea might be fine for a feed or two, even a welcome change, but it doesn't contain everything needed
Mix it up to get the same balance: commercially prepared products likely already have potassium and sodium in them, so an example of a decent alternative would be a nice warm tea + baby food pouch = fuel, electrolytes and fluids. What other alternatives can you come up with that are palatable to your swimmer? Write them down on the feed plan!

13.3 Monitoring vomiting

Different bodies handle things differently, simple as that. An ultra-marathon swimmer with years of experience under their swimsuit might be able to handle vomiting feeds up repeatedly because they've built up physical resilience to it, whereas someone doing a big marathon swim for the very first time may not know how to manage the likely drop in energy or be able to get adequate fuel, fluids and electrolytes back into their body afterwards in order to keep going for long safely.

Vomiting empties the swimmer’s stomach contents, which would contain both 20-100ml of stomach acid and whatever feeds they have consumed that have yet to be emptied from the stomach into the small intestine. The problem with vomiting is that the swimmer will no longer have that feed available to later turn it into usable energy, absorbed fluids and electrolytes, but also stomach acid is considered part of the body’s fluids and is itself comprised in part of water and electrolytes. By losing both the feeds and the stomach acid, the swimmer’s fluid and electrolytes may now be out of balance and may also be in deficit. The contracting of the diaphragm and stomach muscles can take a lot out of a swimmer as well, leaving them fatigued.

The crew should also be mindful that vomiting can be embarrassing for the swimmer, they need to be facing the crew at feed stops so that the crew can assess what's happening. The crew should take care to treat the swimmer as they normally would, don't react to the process, help support them emotionally if needed, tell them to take their time, etc.

Often a swimmer who vomits will be hesitant to put anything into their body right away afterwards, yet they need to keep moving and will probably try to keep up with the same energy output. The goal would be to find ways to get the swimmer back on track with hydrating and resuming feed intake as soon as possible, or they could wind up in an energy, fluid or electrolyte deficit that could end the swim early or even have serious medical implications.

Here's what might happen with vomiting:

Feeds aren't sitting right or staying down anymore, for any of the reasons in the feed section above
Fumes from the boat might be making them feel sick
Rough water conditions might be giving them motion sickness and making them barfy
A serious health condition such as dehydration or declining kidney function might be the underlying cause

What might be happening to the swimmer's body:

The swimmer may gets much-needed relief, because what was in their stomach wasn't happy
The swimmer may recover easily and keep going, keep going and feel like crap, or need to stop all together
The swimmer may not be able to take in feeds afterwards and are no longer getting adequate fuel, electrolytes, fluids
If the swimmer can't take in fuel, their energy level will drop and their swim speed will likely eventually start to slow
If the swimmer can't take in fluids and electrolytes, they become further at risk for dehydration, sodium and/or potassium imbalance or deficit. Water goes where the salt is, if the swimmer drinks lots of water without electrolytes it could make their blood less salty, water will then enter their cells (hyponatremia). The opposite is dehydration and minimal or no fluid intake, and the swimmer's blood would be saltier than their cells, water will then exit their cells (hypernatremia) and enter the bloodstream. Potassium loss (hypokalemia) happens by not ingesting enough potassium or by excessive filtration in the kidneys.

Things for the crew to consider:

How often are they vomiting? What's the possible cause? How bad might the deficit be?
Fluids, electrolytes: see above Section 13.2 Monitoring feeds, and prioritize rehydrating and resuming feed intake
Fumes: see if they can change sides of the boat or position alongside the boat (they won't be allowed in front of or behind it)
Rough water: does the swimmer take anti-nauseants? Did they test beforehand to be sure it won't make them sleepy?
Serious health condition: marathon swims can be hard, but no swim is worth dying for - live to swim another day

13.4 Monitoring urination

Regular urination is important for any athlete, especially so for marathon swimmers who consume most of their fuel in the form of fluids consumed at very frequent intervals. Some swimmers can pee while swimming, whereas others can only pee when upright on a feed stop. Some swimmers can pee freely, others need to pause and focus. It helps to know a little about how urination works...

Here's how the human body works:

The kidneys are continuously working and producing urine.

The bladder is never really empty, even after urination a healthy bladder will still have 50ml or less of residual urine left in it, with more being added as the kidneys continually do their job. The bladder can hold about 500ml of urine, although it can stretch a bit to hold a little more.

Someone who is very dehydrated could take up to 9-10 hours to drink and produce urine, but someone who is hydrated and has been drinking regularly and has a nearly full bladder will need to pee about 5-15 minutes after consumption. It's hard to be exact, so a good general assumption is the need to pee would probably happen 30-60 minutes after consumption.

It's recommended to not drink more than 1 litre of fluids per hour, to give the kidneys time to process what it needs and flush out the excess into the bladder as urine, to be peed out. The volume of liquid fuel taken by swimmers varies, but let's assume 8-10oz every 30 minutes, so within the 1 litre mark.

Swimmers can sweat in the water and expel some of that, rate of sweating depends on how warm the water and ambient conditions are, how fit the swimmer is and how hard the swimmer is working, so it's impossible to say how much fluid loss is sweat. Unless the swimmer is powering at top speed or under a hot sun, they may not be sweating as much as you think.

Urine travels from the kidneys through ureters (narrow tubes) and into the bladder. When the bladder is full, it sends a signal to the brain, which tells the bladder to contract and sphincter muscles to release, allowing urine to travel out through the urethra.

What happens if you're not peeing regularly? 8-10oz every 30 minutes + no peeing for hours = a very full bladder, with more fluid being forced into it at each feed stop. Bladder muscles can then get overstretched and damaged, and a full bladder with nowhere for urine to go can result in the urine going back up the ureters and flooding the kidneys, causing swelling and potentially kidney damage.

Acute kidney failure can develop rapidly, within hours to a few days, and kidneys are no longer able to adequately filter waste and excess fluid from the blood. This needs immediate treatment to prevent long-term damage.

Here what might happen with urination:

The swimmer may experience a gradual decrease in volume or sudden cessation of urination.
The swimmer may decrease their intake of fluids and electrolytes, resulting in the changes to their urination
The swimmer may continue to consume fluids and electrolytes, and still not be able to pee much or at all
The swimmer may feel fatigue and weakness, and experience nausea and vomiting
The swimmer may exhibit confusion or difficulty concentrating

What might be happening to their bodies:

Dehydration
Electrolyte imbalance and/or deficit
Significant fluid and electrolyte loss through sweating
Decrease in kidney function

The crew should ask the swimmer about typical urination rate on long swims and whether there are any pre-existing medical condition affecting urination they should be aware of. On the swim, ask the swimmer when they last urinated and note it on the crew/observer log so that you keep track. You can ask the swimmer verbally on a feed stop or write “Last time you peed?” on the whiteboard. If lack of urination becomes a concern, keep encouraging the swimmer to try releasing, even if it makes the feed stop longer - and if they can't, this may become a swim-ending issue.

13.5 Monitoring cognitive function

There are simple cognitive tests you can use on the swimmer if you're concerned about their cognitive function, add them to the written swim plan if you're doing one. They can be given to the swimmer on feed stops, or in between if you suspect something is going seriously wrong. You can discuss the tests with the swimmer ahead of the swim, even arrange to get simple questions and answers written down, but then try to avoid letting the swimmer rehearse the answers to questions because you’re trying to test their cognitive ability in the moment. Keep testing until you feel you can assess the swimmer's state of well-being.

Simple cognitive tests:

Verbal direction: "touch your nose with your right hand”, “place your right hand on your left knee.”
Attention and concentration: spell a five-letter word forward and backward, "waves", "start"
Reasoning: complete a simple math problem, “what is 2+5?”
Memory: ask simple questions you know the answers to or can find out for sure, "What's your cat's name?"