Training for marathon swims: Pool vs. open water

Newbie marathon swimmers often wonder how they should allocate their training time between the pool and open water. There’s no simple answer: It depends on a variety of factors unique to the individual. A few questions to ask yourself:

What’s the target swim? Distance, water temp, conditions, etc. The further outside neutral conditions your target swim is, the more open water you’ll want to incorporate into your training. (To train for cold water… swim in cold water.)

Are you training to finish (regardless of time), or are you training to race? The more speed matters in your target swim, the more high-quality interval training in the pool you’ll probably want to do.

What’s most convenient? If you live next to a safe body of open water, but far away from the nearest pool, this may tip the balance towards OWS. In my experience, convenience promotes consistency — and consistency promotes results.

What do you inherently enjoy? If you have access to a high-quality Masters pool squad with good coaching and fun lanemates, this may tip the balance towards the pool. If you get blissed out by open water, this may tip the balance towards OWS. Enjoyment promotes consistency, and consistency promotes results.

Consistency is the main thing, and I’d say whatever formula helps you swim consistently is fine.


For the sake of argument, though, let’s say convenience and enjoyment don’t pose obstacles for you. All else being equal, what’s the ideal combination of pool & open water training?

My personal beliefs are, you can’t beat the pool for improving speed and stroke technique; and you can’t beat open water for acclimating to cold water and rough conditions.

Perhaps that’s just common sense. But there are some less-obvious corollaries:

In my opinion, for many mainstream marathon swims it’s perfectly OK to do most of your training in the pool. When I did the 24-mile Tampa Bay Marathon Swim in April 2011, I hadn’t been in open water since the previous October.  I won by 42 minutes.

I don’t mean to say open-water training isn’t valuable or important; but I do think sometimes marathon swimmers underestimate the value of pool training.

In that vein, I was struck by this recent tweet from Swim Smooth founder and 2013 MIMS champion Paul Newsome:

Like me, Paul comes from a pool-swimming background, but as an adult competes primarily in long-distance open water swims. Like me, he does most of his training in the pool, even for moderately “cold” swims such as MIMS 2013 (61F).

Among elite professional open water swimmers, the ratio of pool to open-water training approaches 100%. In the case of my old friend Mark, who competed in the Beijing Olympic 10K, his pool training didn’t “approach” 100% – it was 100%. Aside from organized races, he did literally zero open water training in preparation for the Olympics.

What are the exceptions to this rule? You probably already know the answer: very long, very cold swims. You must acclimate. The colder and longer the swim, the more longcold water training you should be doing. For me, anything below about 18C (64.4F) for marathon distance, and I’d aim to be doing at least some of my training outside the warm pool, in cold water. At 15C for the target swim, I’d spend proportionally more time in open water. At 12C, even more. Body fat will also be a factor here.

But still, even for long, cold swims — I probably wouldn’t let my ratio of pool-to-OW training go below 50%. The pool is just so, so much better for developing (and maintaining) speed and fitness. The extra speed (resulting in faster times) and extra fitness (resulting in the ability to maintain higher energy output for longer), more than make up for the opportunity costs in cold-water acclimation.

Taking liberty with a well-known proverb:

All OWS and no pool makes Jack a slow swimmer-boy.

How to get an effective workout at public lap swim

This post is part of a collaborative project with Donal at LoneSwimmer, delving into basic issues of training and technique in swimming. Donal also published a post today, check it out here.


Whenever possible, I prefer swimming with other people – either with a training partner or in a coached squad workout. But occasionally my schedule dictates finding water at a public lap swim session. It’s possible to get a good workout at open lap swim, but it takes a bit of planning and training know-how.

Based on my observations at hundreds of public lap swim sessions over the years, there are some folks who come to swim laps, desire to become better swimmers, but simply don’t know how to go about the task. For those without a background in competitive swimming or similar sport, it may not be at all obvious.

For example, one of the more common approaches I see at the pool consists of: (1) Getting in the water. (2) Swimming continuously for X amount of time. (3) Getting out.

With that in mind, here are a few pointers on getting the most out of solo workouts at a public lap swim session:

Learn proper lane etiquette.

It will be less frustrating for you… and everyone around you in the pool.

Have a workout plan.

Not necessarily a full written workout with every detail, but at least a basic mental structure of a workout. What do you want to accomplish today?

A basic workout structure can be as simple as this:

  • Warm-up – mostly easy swimming.
  • Technique work & build into main set.
  • Main set.
  • Kick or pull set.
  • Cool-down.

Interval training is more efficient than continuous swimming.

Continuous low-intensity swimming is an inefficient way to build cardiovascular endurance. Interval training (repetitions of shorter distances, swum at higher intensities than one could sustain continuously) is far more effective.

Check out the Marathon Swimmers Forum for some good example interval sets:

Don’t rely on pool gear.

Fins, paddles, buoys and snorkels are swim tools, designed for specific purposes, typically strength or technique-related. When you use any swim tool for an entire workout (or majority of it), it’s no longer a tool but rather a swim aid.

If you can’t swim without fins, in my view, you can’t swim. What happens when they fall off accidentally in the ocean? If you always strap on paddles for the main set, what happens when you compete and you can’t use your paddles?

Learn flip turns – even if you only compete in open water.

If you do open turns, you’re basically coming to a complete stop between every length of the pool. Open turns are surprisingly common among triathletes, even relatively fast ones. I’ve never understood it; plus it looks goofy. Flip turns (sometimes called tumble turns) allow you to transfer much more momentum from one length to the next. It makes pool swimming much more bearable.

Learn all four strokes – even if you only compete in freestyle/front-crawl.

Different strokes work different muscle groups, and it will make you a better athlete. Backstroke can provide a nice change of pace for your shoulders after too much front-crawl.

Controlled Stroke Count Drill

In “Stroke Count Games” and “A Better SWOLF Formula” I suggested a test set of 8×100, as fast as possible, holding a specific number of strokes per length (SPL), to hone in on your most efficient combination of stroke length and tempo.

I frequently do a modified version of this set as a quick tune-up before a competition or a challenging distance workout: 12×100 short-course, aiming for the following SPL on each rep: 15, 14, 13, 12, 11, 10, 10, 11, 12, 13, 14, 15. Moderate, controlled pace on all – no more than 75%.

Obviously, the specific SPL goals will differ for each individual. For me, 15 SPL is my 400m/500yd race pace. 14 SPL is my 1-2 mile race pace. 13 SPL is my marathon pace.

The reason I like this set as a warm-up / tune-up is that the act of “depriving myself” of one stroke-per-length on each of the first 6 reps really focuses my attention on efficiency – maximizing the amount of water I’m pulling, and minimizing drag. Then, adding one SPL on the way up (11, 12, 13, 14, 15) feels increasingly luxurious and powerful.

The over-arching goal: the 13, 14, and 15 SPL reps on the way up should feel better, faster, and more efficient than the 15, 14, and 13 SPL reps on the way down.

I took some GoPro video of myself doing this set, so you can see the subtle differences in my stroke from one rep to the next. The video shows a bottom-of-the-pool view of me descending from 15 to 10 SPL; then a side-underwater view of 14 SPL; then an above-water view of 14 SPL.

(Direct link to video)

A better SWOLF formula

SWOLF (“swim golf”) is a drill that measures swimming efficiency. A SWOLF score is your time (in seconds) on one lap of the pool, added to the number of strokes you took. Lower scores = Higher efficiency. SWOLF is a fuzzy, indirect measure of efficiency, because stroke count doesn’t necessarily reflect effort. In my view, the most precise definition of SWOLF is that it identifies the most efficient stroke count for a given level of effort.

I originally wrote about SWOLF in April 2012, and the post has become – by a wide margin – the most widely-read in the history of this blog. In a subsequent post a month later – “Stroke Count Games” – I described how SWOLF doesn’t quite capture the most efficient stroke count. At least for me, using stroke cycles (number of strokes divided by two) produces better results.

I wondered if this was true for other swimmers, so I asked any interested readers to send me their own data, using a test set of 8×100. Three readers sent me their results. In short, my suspicions were confirmed: Strokes cycles produces better results than stroke count. In essence, the original SWOLF formula seems to over-weight stroke length in its measure of efficiency (and thus under-weight speed).


Reader #1 is a 6-foot 2-inch (188 cm) male in his late-20’s with an ape index of 1.07 (arm-span greater than height). He did not swim competitively at the high school or college level. His recent best times include 25:21 for the 1650-yd Freestyle and 3 hours, 18 minutes for a 10km open-water swim. His typical open-water stroke rate at marathon pace is approximately 50 strokes per minute.

Here are his results for the test set of 8×100:

SPL m:ss SWOLF SWOLF-improved
10 1:50 150 130
11 1:40 144 122
12 1:30 138 115
13 1:23 135 109
14 1:16 132 104
15 1:12 132 102
16 1:13 137 105
17 1:15 143 109
18 1:17 149 113

Reader #1 pegged his “natural” stroke count per 25 yards at 15-17. According to traditional SWOLF, he was most efficient at 14-15 SPL, followed by 13. According to SWOLF-improved, he was most efficient at 15 SPL, closely followed by 14 and 16 SPL. SWOLF-improved seems slightly more accurate in this case. In Reader #1’s own words:

15-17 feels natural.  At 14 I could already notice some laboring.  Anything at 13 or lower, inertia was a huge factor.

I think that’s why the curve is much steeper on the lower stroke side.  It might have said 13 was more efficient than 17, but no way I’d want to swim more than a 100 at 13.  17 – no problem.


Reader #2 is a 5-foot 7-inch (170 cm) female in her late 20’s with an ape index of 1.0 (arm-span equal to height). She swam competitively in both high school and college, and is a Triple Crown marathon swimmer. Her recent best times in the pool include 19:15 for the 1650-yd Freestyle. Her typical open-water stroke rate at marathon pace is 70 strokes per minute.

Reader #2 insists her data include the caveat that she did a big training swim (21km) the previous day 😉

SPL m:ss SWOLF SWOLF-improved
15 1:20 140 110
16 1:18 142 110
17 1:15 143 109
18 1:12 144 108
19 1:10 146 108
20 1:08 148 108
21 1:08 152 110
22 1:10 158 114

Reader #2 puts her “natural” stroke count per 25 yards at 18-20, depending on pace. SWOLF-improved agrees. Traditional SWOLF, on the other hand, under-estimates her most efficient stroke count.


Reader #3 is a 5-foot 6-inch female in her early 20’s. She swam competitively in both high school and college, and is a national-caliber distance swimmer. Her recent best pool times include 17:09 for the 1650-yd Freestyle. Her typical open-water stroke rate is approximately 80 strokes per minute.

SPL m:ss SWOLF SWOLF-improved
12 1:14 122 98
13 1:10 122 96
14 1:08 124 96
15 1:04.5 124.5 94.5
16 1:02 126 94
17 1:00 128 94
18 0:59.5 131.5 95.5
19 0:59 135 97

Reader #3 puts her “natural” stroke count per 25 yards at 16-17. SWOLF-improved agrees. Traditional SWOLF, once again, underestimates the most efficient stroke count.


For comparison, here are my results from the 8×100 set, as reported previously:

SPL m:ss SWOLF SWOLF-improved
9 1:20 116 98
10 1:14 114 94
11 1:10 114 92
12 1:07 115 91
13 1:05 117 91
14 1:02 118 90
15 1:00 120 90
16 1:01 121 93

In sum, you may find that using stroke cycles instead of stroke count produces more useful SWOLF results. If you own a Swimsense, then you’re golden – it already uses stroke cycles for its SWOLF calculation. I don’t own a Garmin Swim watch, but from what I’ve read online it seems to use the traditional formula.

Should you use swim paddles? A rule of thumb

Swim paddles (in my opinion) are useful for developing swim-specific strength, especially in the shoulders and lats. I prefer Strokemakers:

strokemaker paddles
Strokemaker paddle (size red #3). NOTE: The paddles come with a longer strap meant for the wrist, but don’t use it. That’s goofy. If you need the wrist strap to keep the paddle stable, you’re doing it wrong.

Strokemakers are the classic paddle for competitive swimmers. At various points in my swimming career I’ve used Green #1sYellow #2sRed #3s, and Blue #4s. As a Masters swimmer, I use Reds. As an open-water and marathon swimmer, I feel that the strength I develop with these paddles (which some have derogatorily described as “dinner plates”) helps me power through waves and chop in rough-water conditions.

(Note: I have no financial relationship with the company that makes Strokemakers. Every one of their products I own, I’ve paid for. I just like their paddles.)

There’s a catch, though: It’s probably a bad idea to use these paddles as a beginning (or even intermediate-level) swimmer. You can hurt yourself! Certain stroke flaws (thumb-first entry, crossing over the mid-line, dropping your elbows on the catch), combined with paddles, can lead to rotator cuff injuries.

How do you know if your technique is good enough to start using “power paddles” such as Strokemakers?

I’d like to suggest a simple rule of thumb: If you can swim with the FINIS Agility paddles without struggling to keep them on your hands, your technique is probably good enough for power paddles.

Karen has a nice description of how the Agility paddles “test” your technique.

Important caveat: If at any point you develop shoulder pain while using paddles, stop using them immediately!

finis agility paddles
FINIS Agility paddle. Hand not included.

I received a complimentary pair of Agility paddles from FINIS at Jamie’s swim camp a few months ago. I have no trouble keeping them on, but I still use them occasionally because of how well I can feel the initial “catch” of my stroke. I think of the Agility paddles as feel for the water paddles, in contrast to the Strokemaker power paddles.

I was happy to hear recently that FINIS is now selling three sizes of Agility paddles – small and large, in addition to the original size (now called “medium”). I always felt the original Agility paddles were a bit too small for my hands, so if I were in the market for new ones, I’d get the Large.

One final note: as usual, I find Terry Laughlin’s perspective on this to be overly simplistic and dogmatic.

Whirlpool Drill

Whirlpool Drill is one of my very favorite swimming drills – yet when I’ve shown or told people about it, I’ve been surprised how few have heard of it. It’s so much fun it almost seems like it shouldn’t be a drill. So here I am, sharing the wealth.

The other day I was doing a filming session off Santa Cruz Island (more on that later), and Whirlpool Drill was accidentally caught on tape! I was treading water, talking to one of the filmmakers, and a little whirlpool started to form near one of my hands. I got my interlocutor’s attention and made the whirlpool bigger for a few seconds while he kept the GoPro running. At one point, a stray piece of kelp was drawn into the vortex. Here’s the clip:

Basically, you scull your hand back and forth a few inches under water – rapidly, trying to maintain constant pressure against the water. If you’re doing it right, you’ll make a whirlpool! Bonus points for big and/or long-lasting whirlpools. Extra bonus points for keeping two of them going – both hands, at the same time!

Whirlpool Drill is basically a more focused, intense form of the various sculling drills, which are intended to reinforce a solid catch and “feel for the water.”

How big is your whirlpool?

Good Workouts and Bad Workouts

100×100 may be “the most famous of all distance swimming sessions” – but I’d never actually done it… until last Friday. Mark invited me to his USA-S squad’s morning practice, for reasons unspecified, and had this “special surprise” waiting for us: 100×100 (SCY), as:

  • 10 @ 1:30, warm-up
  • 10 @ 1:20
  • 10 @ { 2 @ 1:15, 3 @ 1:10, 3 @ 1:20, 2 @ 1:30 }
  • 6x: 10 @ { 4 @ 1:10, 3 @ 1:30, 2 @ 1:05, 1 @ 2:10 }
  • 10 @ 1:30, cool-down

Normally this would be a make-able (if challenging) set for me. Unfortunately, Friday was not a normal day. For whatever reason, my body was just not cooperating. I lifted weights on Thursday, but I don’t think that entirely accounts for it. It was just one of those days.

I have a “lead balloon” day once a month or so. I recognize it within minutes of getting in the water. Wow… I’ve got *nothing* today. On such days, I usually adjust my plans. Slow drilling, sculling, kicking… anything but a distance-overload set on tight intervals.

By the second round of 10×100 (1:20 interval), it was clear I was having “one of those days.” My body position felt off. I was having trouble hitting my stroke count (14), which on a normal day I can do with my eyes closed (literally). I was approaching the wall in-between strokes (e.g., 14 & and a half), and thus either jamming or floating my turns. It didn’t help that I was swimming in an end-lane without visual targets on the walls. One time I actually “whiffed” on a flip-turn – like, I totally missed the wall – which I can’t remember ever doing, even when I was 7 years old.

I was a mess.

And yet – at the end of that second round, I still had 80x100s to go! 240 flip turns. Ugh. If this were a solo workout, I’d probably try to get through an hour and call it a day. If this were Masters – probably the same. But this was different. When you swim with kids half your age, your pride is at stake. You can’t just bail a third of the way through the workout.

So, I kept swimming. I didn’t make every send-off, but I completed every lap. If you look at the “main set” of 60×100, you’ll notice every 10th repeat is on 2:10 – providing a buffer for those who missed one (or both) of the 1:05 send-offs to catch up. This buffer was my saving grace.

As much as possible, I tried not to struggle. I focused on good technique – on trying to feel smooth, even if I felt like a lead balloon. My goal was to finish 10,000 yards without hurting myself. As much as possible, I ignored the clock. Speed was a secondary consideration.

Much like a channel swim, actually. In my younger, pool-swimming focused days, I might have considered this a “bad workout.” In pool swimming, “good” and bad” is defined by speed. In a channel swim, though, the primary consideration is: Did you make it across? Did you keep swimming for as long as it took?

And in that sense, this was a useful workout. Not a “good” workout, exactly… but a useful one.