By Mel Donaldson, High Performance SwimMastery Coach
Last month I swam 20km at Caramoan in the Philippines on about four weeks of preparation, most of it technique. I finished injury-free, my shoulders were happy, and I loved the back half.
People expect a marathon swim to need months of grinding out kilometres. After 20+ years of coaching, and my own marathon swims of 16 to 26km, I can tell you: more is not always better. Often it's worse.
Training is a bank account
Every hard session is a withdrawal. Rest, sleep, good food and mindful, unhurried swimming are the deposits. Fitness is the interest, and it only builds while the account stays in credit.
Keep withdrawing without depositing and you slide into overdraft. In swimming we call that overtraining: flat mood, heavy arms, niggly shoulders and times going backwards.
The science agrees. In a classic study, swimmers who doubled up to twice-daily sessions got no fitter than those training once a day, and actually lost speed (Costill et al., 1991). Another study of 400 swimmers found their mood dipped as the training load rose, then bounced back when it eased (Morgan et al., 1987). Your mood is often the first statement from the bank.
Stop pouring water into a leaking bucket
Imagine filling a bucket full of holes. You can pour faster, pour longer, pour harder, and the water still drains out the bottom. That's what extra kilometres do for a leaky stroke.
The holes in your body are things like a dropped elbow, a crossover, a fighting kick or a lifted head to breathe. Each one leaks a little energy. Over the tens of thousands of strokes in a marathon swim, those little leaks empty you by hour five. And your shoulders usually pay the price.
The holes in your mind are just as real. Tension, rushing, worrying about the finish, chasing the swimmer beside you. Each one burns energy and quietly pulls your stroke apart.
More training doesn't fix a leaking bucket. Patching the holes does. That's why technique sits at the heart of SwimMastery: every lap is a rehearsal, so make it a good one. Plug the leaks, and the same training suddenly fills you up.
What the best endurance athletes know
The world's best endurance athletes don't just pour more in. Elite cyclists, Tour de France winners included, do around 80% of their riding at low intensity (Seiler, 2010). The Norwegians, who've produced Olympic and Ironman champions, are known for "double threshold" days. But their real secret is restraint: they keep hard sessions just below the red line so they can come back and do it again tomorrow.
The trap most of us fall into is making every session a bit too hard to be easy and too easy to be truly hard. It feels productive. Mostly, it's just tiring.
Mindful swimming: one cue at a time
So what do you do instead of piling on kilometres? Swim mindfully. Pick three technique cues for a set, such as sending your head away from your feet, a light/consistent flutter, streamline left/streamline right and give your full attention to one cue at a time. When it feels natural, move on to the next. One cue at a time is how a patch becomes permanent.
What you're really training is proprioception: your body's sense of where it is and what it's doing. In the water, we call it feel for the water A few findings worth knowing:
Fatigue switches feel off. After tiring shoulder exercise, people needed 73% more movement before they could even detect their shoulder moving (Carpenter et al., 1998). Swim exhausted and you can't feel the leaks, let alone fix them.
Where you focus matters. Swimmers who focused on "pushing the water back" swam faster than when they focused on their hands (Freudenheim et al., 2010). The best cues are about the water, not your body parts.
Feel can be trained. In a 2025 trial, elite swimmers who added eyes-closed imagery to their core exercises sharpened their body awareness more than those doing the exercises alone (Solana-Tramunt & Bofill-Ródenas, 2025).
It's a mindset as much as a technique: a quiet, curious mind notices the leaks. A rushed, tired one never does.
It's why we named my business At One Swimming rather than reaching for the word "mindful". For us, great swimming is being at one with the water, mind and body together. No fighting it, no leaks, just you and the water moving as one.
What you need to know for a marathon swim
Technique first. Efficient strokes save energy and shoulders.
Swim mindfully. Most sets should be unhurried, with your attention on one technique cue at a time.
Control the hard work. One or two quality sessions a week, done with control rather than heroics.
Build slowly. Add no more than about 10% a week, with a lighter week every three to four weeks.
Rehearse race day. Open water swims with your feeding plan, sighting and race gear.
Never swim alone. Bring a buddy, a kayak or a support boat.
Listen to your mood and shoulders. Flat, cranky or niggly means rest, not more kilometres.
Taper and recover. You get fitter while you rest.
I'm currently planning my next open water swim. It won't be about distance but technique, because that's exactly what carried me through 20km at Caramoan. The kilometres take care of themselves once the bucket stops leaking. So every session, I'll be hunting for one more hole to patch, in my stroke and in my head. I'd rather stand on the start line with a stroke I trust and a calm mind than with a logbook full of tired kilometres.
If you're eyeing your first 10km or your next marathon swim, come and patch your bucket with me at our Swim Studio in Sumner, Brisbane. We will introduce you to THE SWIMMASTERY technique in our Endless Pool with underwater cameras to show you exactly where the leaks are.
— Melissa
Further reading
Costill, D.L. et al. (1991). Adaptations to swimming training: influence of training volume. Medicine & Science in Sports & Exercise, 23, 371–377.
Morgan, W.P. et al. (1987). Psychological monitoring of overtraining and staleness. British Journal of Sports Medicine, 21(3), 107–114.
Seiler, S. (2010). What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance, 5, 276–291.
Culp, B. (2024). The Norwegian Method.
Carpenter, J.E., Blasier, R.B. & Pellizzon, G.G. (1998). The effects of muscle fatigue on shoulder joint position sense. American Journal of Sports Medicine, 26(2), 262–265.
Freudenheim, A.M., Wulf, G. et al. (2010). An external focus of attention results in greater swimming speed. International Journal of Sports Science and Coaching, 5(4), 533–542.
Solana-Tramunt, M. & Bofill-Ródenas, A. (2025). Motor imagery enhances core training effects on lumbar proprioception in elite swimmers. Frontiers in Physiology, 16.