Open water swimming training: sighting, drafting, pacing, and pool sessions that get you ready

Open water swimming is pool swimming without the things that keep you on track: no lane lines, no black line on the bottom, no wall to push off or rest on. The American Red Cross puts the gap plainly: being water competent in the ocean requires stronger and different skills than in a pool.¹ A 2017 review of open-water swimming research adds that open-water races may bring extreme conditions, such as water temperature, tides, currents and waves, that affect performance, tactics and pacing, and that specific studies of these events are scarce.²

This page covers the skills to practise, what the studies measured for drafting, pace and wetsuits, two pool sessions, and a practical week. The studies were in swimmers, trained triathletes and elite racers, so read them as how open water works, not as a measurement of you. It's a training page: it makes no health claim, and safety, cold water and heat are left to the sources that cover them. The pool basics are on a swimming workout.

Before the training: where, and with whom

The Red Cross's beach and ocean guidance starts with two rules: always swim in a lifeguarded area, and never swim alone, regardless of your age or level of swimming skills.¹ U.S. Masters Swimming adds a plan: let someone know where and when you're swimming, how long you'll be gone, and when you plan to return.³ The same Red Cross page covers currents, waves and rip currents. Read it there; this page doesn't repeat it.

Sighting: looking where you're going

U.S. Masters Swimming describes sighting as raising your head to see where you are, and the hard part as keeping your legs from dropping when your head comes up. Its technique, in short:⁴

• Pick a fixed point. A building or a tree on shore, or the next buoy, and swim as straight a line to it as you can.
• Crocodile eyes. Lift your head just enough to see above the water line, keeping the bottom half of your face in the water, then put it straight back down. Breathe separately, to the side as usual.^4,3
• Keep the legs up. As you look, push down a little harder in the catch of the stroke and kick a little harder to keep your feet at the surface.
• How often. In a race, about every eight to 10 strokes. On a relaxed training swim you can space it out, but still look up regularly for anything ahead. In rougher ocean conditions, look up higher to clear the waves, and sight less often.

Practise it in the pool first. USMS suggests sighting twice in each length during a set of 4 x 100.⁴

Swimming straight without a line

USMS points out that everyone swims in a circle, because no one is perfectly symmetrical; the difference is how wide the circle is.³ A pool drill to find your drift: close your eyes for 6 to 8 strokes, open them, and see how far you've pulled to one side. Most swimmers have a side they drift toward, and knowing it is what lets you correct it.⁵ Two other strokes help: a decent breaststroke lets you look forward on every breath to correct your course, and an efficient backstroke helps when you need to rest or clear your goggles.³

Drafting: what swimming behind someone changed

Drafting is swimming close behind or beside another swimmer. Four studies measured it, in swimmers and triathletes:

• How far behind. In 11 swimmers at 95% of their best 1,500 m pace, oxygen uptake, heart rate, blood lactate, perceived exertion and stroke rate were all lower in every drafting position than swimming alone. Drag fell most right behind the lead swimmer's toes, 0 to 50 cm back, by 21% and 20%; to the side, it fell 6% to 7% at 50 to 100 cm back from the lead swimmer's hands.⁶
• Behind or beside. In a second lab study, drafting behind an active lead swimmer cut passive drag by 9% and oxygen uptake by 11%; at the side, drag went up 8% and oxygen uptake barely changed. The authors' pick was directly behind, about 0.5 m from the lead swimmer's toes to the drafter's hands.⁷
• Over 400 m. Eight highly trained triathletes swam 3.2% faster drafting, with lower blood lactate, a lower stroke rate and longer strokes; the faster and leaner swimmers gained more.⁸
• The effort. In seven trained male swimmers over 549 m at 95% of their maximal speed, drafting lowered oxygen uptake, blood lactate, perceived exertion and heart rate.⁹

Read together: right behind a steady swimmer's feet, the same pace costs less, and swimming beside them doesn't do the same. Swimming that close without bumping takes practice; USMS suggests swimming in a tight pack with your lanemates in the pool to get used to it.¹⁰ Whether drafting is allowed in a given event is that event's rule, not covered here.

Pace: from the pool clock to open water

Expect open water to be slower than the pool. U.S. Masters Swimming's rule of thumb: with no walls to push off, your pace per 100 is roughly 5 seconds or more slower, and adding about 10 seconds per 100 is a good basic estimate, with wind and waves slowing you further. Its example: a 500 in 8:00 in practice is 1:36 per 100, so about 1:46 per 100 in open water.¹¹ It's a ballpark, not a measurement.

In the one study here that compared the two, 14 elite triathletes swam 1,500 m in open water and in a 25 m pool. In open water their strokes were shorter and quicker (lower stroke length, higher stroke rate), while heart rate, blood lactate and end-of-swim oxygen uptake didn't differ, and the fastest in open water were also the fastest in the pool.¹² So the pool is a fair place to build open-water fitness, and the stroke changes are the part to practise outside.

On pacing a long swim, a study of 1,206 elite race performances over 5, 10 and 25 km found that the swimmers who finished within 0.5% of the winner swam a negative split, speeding up over the last part of the race.¹³ Those are elite international racers. The practical version for a training swim: start at an effort you could hold for much longer, and pick it up at the end. Go by effort rather than heart rate, because heart rate runs lower in the water.

Wetsuit or not: what two studies measured

In 33 swimmers doing a maximal 400 m in a 25 m pool, a wetsuit cut their time by about 6%, and the gain came from a longer stroke, about 4% more distance per stroke.¹⁴ In 11 national- and international-level triathletes swimming 7 x 200 m at a fixed speed, the wetsuit lowered heart rate, perceived exertion and the number of strokes, kicks and breaths, with no difference in how comfortable they felt swimming.¹⁵ Both are performance measurements, not advice on when to wear one: water temperature and the event's rules decide that. In warm water, heat is the bigger question (working out in the heat).

Two pool sessions that get you ready

Practical, not protocols from a trial; the drills come from U.S. Masters Swimming's pool-to-open-water articles.^4,5,10 "Steady" means a pace you could keep going at for a long time.

If you're new to swimming without stops, build the continuous swim first. USMS notes that open water is continuous, with no resting on the wall, and advises starting with shorter distances and working your way up.³ Write the sessions down (the workout log).

A practical week

Practical: two pool sessions, one open-water swim, and strength work on two days. The World Health Organization asks adults for muscle-strengthening activities on 2 or more days a week,¹⁶ and the lifts for swimmers are on strength training for swimmers.

When the continuous swim feels easy, make it longer before you make it faster.

Open water in South Florida

Diogo Camera is an online fitness coach based in South Florida, where an ocean swim is on the table most of the year and the heat is the part to plan around: NOAA's 1991–2020 normals put the Miami International Airport station at 91.4 days a year at or above 90 F.¹⁷ Working out in the heat covers what heat does to a hard effort, and the Red Cross page above covers the ocean itself. Paddling has its own page: kayaking workout. Coaching is online, wherever you swim: online coaching in Florida.

Common questions

How do I train for open water swimming?

Build a continuous swim and the open-water skills in the pool (sighting, swimming straight, starting without a wall, drafting), then swim in open water with a buddy, in a lifeguarded area.^5,1 The week above is one practical layout.

Can you train for open water in a pool?

For most of it, yes. In 14 elite triathletes, the fastest in open water were also the fastest in the pool, though their strokes changed outside,¹² and USMS lists the pool drills that transfer.⁵ The stroke changes and the conditions are what open-water swims are for.

How often should you sight in open water?

About every eight to 10 strokes in a race, by USMS's guidance; less often on a relaxed swim, but still regularly, and adjusted for the conditions.⁴

Does drafting help in swimming?

In these studies, yes: lower drag and lower effort right behind another swimmer, and 3.2% faster over 400 m in triathletes. Beside the lead swimmer, it didn't help in the same way.^6,7,8

Is swimming in the ocean good exercise?

The Compendium of Physical Activities estimates swimming in a lake, ocean or river at 6.0 METs (marked as an estimated value) and a 5 km open-water swim at 10.5, against 5.8 for slow freestyle laps.¹⁸ METs are estimates for an average adult, not a measurement of you; a swimming workout explains the scale. The page makes no weight or calorie claim.

Do I need a wetsuit for open water swimming?

This page doesn't answer that. The two studies above measured speed and effort with one, not when you need one; water temperature and the event's rules decide.^14,15

I'm a fitness coach, not a doctor or a lifeguard: if you have a health condition, ask a doctor before you start swimming in open water, and on the day, ask a lifeguard about the water conditions.¹

If you'd rather have the week planned

Pool days, strength days and an ocean swim that depends on the weather only work when they land in the right order. Coaching is the version where your workouts are built around the days and places you actually train, and a weekly call looks at the week you just had and rebuilds the next one. Coaching explains how it works, and apply is the first step. Otherwise: add the sighting set to your next pool session.