I love swimming in the dark, and used to wake up in the wee hours to meet friends at our local beach long before dawn so that we could swim before the sun came up. With safety in mind, we'd stay close to the shoreline and go back and forth.
But swimming in the dark on a long marathon swim can be an entirely different experience - you're far from shore in pitch black darkness, the movement and lights on the support boat can be nauseating, and for some of us there's a deep shift in what our senses take in.
Tom Heyerdahl, In Search of Memphre 2025
My first solo marathon swim required a 3-hour nighttime qualifying swim, so my dad and sister went out in a motorboat with a bright lantern and headlamp pointed in my direction so I could get a fully uncomfortable experience while I swam. The bright lights were awful, but it did prepare me for the most extreme circumstances. We set out just as the sun went down, and made our way to the middle of the lake. It was a very dark night and calm water, and I was surprised at how different the swim felt. Here's what I noticed:​
-
Reduced visual input in the dark heightened my other senses, I couldn't see or hear much but I felt literally everything
​
-
I was a little more on edge, very focused on the boat, and easily startled by things like unexpectedly swimming into weeds (the locals got a nighttime scream)
​​
-
My emotions were heightened, I was on edge but also excited to experience something new, in awe of how beautiful the dark sky was, how smooth the water felt on my body...it was a lot
​
-
My sense of temperature changed, I felt chilled even though it wasn't cold out, I could really feel the air moving across my arms​​
Crew Kathleene Marcil
I went to bed that night grateful to have finally experience truly dark swimming. The next morning though, I could barely get out of bed to make coffee. I was drained, completely exhausted, and realized the swim had been intense sensory overload. I knew I would have to keep myself in check on the solo swim itself, try to remain calm and not take in quite so much. And so I did, and it went really well, I found the darkness soothing and the rhythm of my arm strokes sent me into a deeply meditative flow state.
​
So yeah, your swimmer might experience some heavy stuff in the dark...
10.2 Brrrrrr....it can get pretty cold at night!
Back to crewing! Nighttime on the water will be different for the crew too, and depending on the time of year it can get pretty cold and humid. Check the weather, consider the humidity, and bring layers of warm clothing so that you can adjust as needed, maybe even a warm jacket or swim parka to throw on if you think it might be needed. You can also put your clothing in a dry bag inside of your backpack to keep off the dew and prevent everything from getting damp, although long narrow dry bags can be hard to get stuff out of when you need it. Find out if the boat will have a heater of any kind. Get dressed and warm before the sun goes down.
10.3 Finding a good headlamp
Crew Christine Herman
Having a headlamp is essential for crewing in the dark, the key is to find one that is bright enough to see what you're doing but won't also blind everyone else on the boat. I bought my first headlamp and spent a little extra to get one that was 1000 lumens, I figured brighter was better. Nope, the moment I turned it on, the boat pilots both flung their hands over their eyes and shouted "whoa!" in unison. And it was only on the lowest green light setting. I couldn't use it at all, and had to borrow the headlamp the other crew member had brought for herself. Lesson learned!
​
The green light was a great idea though, a friend had recommended avoiding white light altogether if possible as it can be especially harsh for everyone on the boat and even the swimmer in the water - bright lights on the boat in the dark can be both irritating and nauseating to a swimmer. So I searched for lower lumen models that specifically had green and red light options - green would be used for prepping feeds or moving around the boat, and red would be our nighttime signal to catch the swimmer's attention and have them stop and remove an earplug so we could talk to them. The problem is, the advertised lumens are for the white light settings, and most manufacturers don't identify on their packaging how many lumens the other colours actually are.
​
I've testing 3 headlamps in total, and landed on the Petzl Aria 1 as my favourite one, it's 350 lumens but has soft green, red AND blue light settings, the green and red are softer than even my 200 lumen Pursuit. You can see in the pics below, the white and red are bright enough to illuminate the front of my shirt, but the green and blue are softer and don't. The green and blue lights on the Petzl are the perfect amount of soft light for me for working on the boat. The other headlamps come along as backups.
​Even if your headlamp has lower lumens, avoid pointing it directly at people when you're wearing it. Instead of wearing it on your head, you could wear it around your neck with the light pointing downwards (pics below, left and middle) and simply point where needed. Either way, the best practice is to simply turn it off when not in use - the less distractions on the boat in the dark, the better.
​
Another option that works well is a small clip light, the one shown here (pic below, right) is only 25 lumens and could be attached to a hat or even better, to the feed bag or clipboard itself so that it's lower to the deck and not shining in anyone's eyes.
10.4 Lighting up the swimmer
Nadine Bennett, In Search of Memphre 2023
​The swimmer will be required to wear lights on them during any swimming that takes place in the dark, and usually the requirement is for 2 lights - 1 attached to the goggles and 1 attached to the lower back of the swimsuit (sewn on or securely clipped on). It’s a good idea to have lights in 2 different colours, so the crew can easily check that the swimmer’s facing the right direction - it's important to be able to make sure they aren't disoriented in the dark, especially if they are getting tired or cold.
Check the advertised battery life on the brand of lights you’re planning to use, but most lights can stay lit for several days at a time, so even if the swim starts in the daytime, the crew can turn them on just before the swimmer gets into the water and not worry about it later when it finally gets dark. Put new batteries in the lights just before the swim!
10.5 Lighting up the feed bottle and feed line
For feeding in the dark, light up the feed bottle and feed line at the same time the swimmer puts their nighttime goggles on.
Attach a bright waterproof light or glowstick to the feed bottle by clipping it to the loop on the bottle or securing it to the bottle with waterproof tape or strong elastics. Hardware stores will carry glowsticks in the boating section that are good and bright too. Keep in mind though, the more you secure to the bottle itself, the harder it is for the swimmer to grip and hold it.
The feed bottle can be heavy when full and will sink partially into the water, making it hard for the swimmer to find it, especially if it lands with the drinking end facing down - and if the lights are attached to the bottle loop on the drinking end, they will get pulled down under the water too. To help with these issues, the feed line can have a small colourful float attached to it, which helps the swimmer spot both the feed line and the bottle.​ An extra light or two can be clipped to the feed line itself near the float as well, if desired. ​​The feed line illustrated here also happens to be glow-in-the-dark, which is handy.​​​
.jpg)
10.7 Why is your swimmer swimming sideways?!
Is your swimmer all over the place, veering towards the boat one minute, then in the opposite direction away from it the next?
The boat is lit up enough that the swimmer can follow alongside it, so what's up with the directional chaos?
It could be disorientation from being in pitch black for hours, but also they might be dozing off a little in the dark. It happens, it's our normal sleepy time after all, but what's surprising is some swimmers can snooze and still maintain a pretty consistent stroke rate thanks to muscle memory and stubborn drive. And that means you can't always tell what the heck is going on...
It can lead to an unsafe situation though, especially if the swimmer isn't responding to signals for feed stops or is further out from the boat than the boat pilots (or kayak and paddler) are comfortable with. On the next feed stop, talk to your swimmer, tell them you need them to focus and stay awake, offer them caffeine if that's an option or ask if shortening the feed stop intervals would help. If you're having a hard time catching their attention to get them to stop to have that conversation, use the brightest white light setting on your headlamp and shine it directly on them, that'll do it...
Justine Brousseau, English Channel 2024 nighttime feed
10.6 Lighting up the start/finish
The boat pilot will likely have a spotlight of some sort to be used for lighting up the shoreline for a dark start and finish, but if you're without one (or you're a big nerd for fun pieces to add to your kit), there are some pretty powerful flashlights out there that work well. The one shown below is 3,500 lumens.
Nadine Bennett, Willoughby 4-Way 2025
Nadine Bennett, In Search of Memphre 2023
Add your own ideas, photos and videos! Send me an email at wildbigswim@gmail.com
10.1 How dark is different
