Open Water Swim Training: How to Prepare When You Only Swim in a Pool

That is why open water swim training isn't simply about swimming more kilometres. It is about removing the things the pool normally does for you.

Why Pool Swimmers Struggle on Race Day

Pool fitness transfers extremely well. Pool habits don't always. A pool gives you a wall every 25 or 50 metres, a clock on the wall, lane markings, and usually very predictable water. You can unconsciously use all of those things to regulate your effort and direction.

Take the walls away, and suddenly you have to make those decisions yourself.

This is particularly important in a triathlon because the swim isn't an isolated event. You still have a bike and run ahead of you. Swimming the first few hundred metres harder than planned because you are caught up in the race can leave you paying for it later.

For a broader look at how to build your overall triathlon preparation, see our guide to How to Train for Your First Sprint Triathlon.

Sighting: The Skill That Separates the Two

If there is one open water swimming technique you should practise in the pool, it is sighting.

You don't need to lift your entire head. In fact, doing that repeatedly will usually make your legs drop and disrupt your stroke.

Try the "crocodile eyes" approach: lift just enough of your face to bring your eyes above the surface, look forward, then immediately return to your normal breathing and stroke.

Start by practising every six to eight strokes.

You can make this even more realistic by putting a target at the end of your lane and sighting toward it without stopping. Once that feels natural, alternate between six, eight, and ten strokes so you aren't locked into one rhythm.

The goal is simple: sighting should become part of your stroke rather than an interruption to it.

Breathing and Staying Calm When It Gets Rough

Open water can make breathing feel completely different.

Cold water, waves, contact with other swimmers, and the simple shock of not being able to see the bottom can all cause your breathing rate to rise. USA Triathlon notes that cold water can contribute to tense muscles and more erratic, shallow breathing.

This is where bilateral breathing can be useful. You don't necessarily have to breathe bilaterally for the entire race, but being comfortable breathing to either side gives you options when sunlight, waves, or another swimmer makes one side less comfortable.

If the water suddenly feels chaotic, don't fight it.

Reduce your effort, settle your breathing, and regain your rhythm. You can even roll onto your back briefly if you need to reset. The objective is to regain control rather than prove that you can push through panic.

Open Water Anxiety Is Normal and Manageable

This deserves more attention than it usually gets. Open water swimming fear isn't a sign that you're unfit or a poor swimmer. The environment is unfamiliar, and your brain is responding to unfamiliar sensory information.

The mistake is trying to overcome that fear by throwing yourself into the middle of a lake and forcing yourself to swim through it. Build exposure gradually.

Your first session might simply involve getting comfortable in the water, swimming for a few minutes, and returning to shore. The next session can include longer continuous efforts, sighting and swimming alongside other people.

Use a supervised venue whenever possible and never swim alone. USA Triathlon specifically recommends asking for help before you become overwhelmed and following the instructions of safety personnel.

Confidence comes from repeated experiences of being uncomfortable, managing it, and discovering that you can handle it.

Pool Sessions That Prepare You for Open Water

You can make your normal pool training much more race-specific without changing everything.

Try incorporating drills such as:

• No-wall swimming: Swim 200–400 metres continuously without pushing hard off the wall. Treat each turn as a simple touch-and-go.

• Sighting sets: Every 6–8 strokes, lift your eyes forward before returning to normal breathing.

• Straight-line practice: Swim without staring at the bottom or lane markings for short sections, then check your direction.

• Tempo changes: Swim 50–100 metres easy, then 50 metres at race effort. This helps you practise changing pace without relying entirely on the clock.

• Deck-up starts: From the side of the pool, enter quickly, settle your breathing, and begin swimming immediately. This gives you a small taste of the disruption of a race start.

These are simple changes, but they teach you to control your swimming rather than relying on the pool to control it for you.

A Simple Four-Week Open Water Swim Training Plan

You don't need to abandon your pool training. Add specificity gradually.

If your race is close, don't try to cram months of open-water experience into one week. A few quality exposures are more useful than one huge session that leaves you exhausted or anxious.

Your First Open Water Session: Do It Safely

Open water is not the place to improvise your safety plan.

For your first sessions:

• Swim at a supervised open-water venue where possible.

• Never swim alone.

• Wear a bright swim cap.

• Use a visible tow float where appropriate.

• Know where you can exit the water before you start.

• Check the water temperature and conditions.

• Tell someone where you are and how long you expect to be swimming.

• Practise with the equipment you expect to use on race day.

Cold water deserves particular attention. Wetsuit requirements vary by race organiser and competition rules, so always check the rules for your specific event. 

Under the 2026 IRONMAN rules, age-group athletes must wear wetsuits below 16°C, while wetsuits are generally permitted up to 24.5°C; USA Triathlon's rules can differ by event.

What to Wear: Wetsuit, Tri Suit, or Both?

If your race permits a wetsuit, most triathletes will wear their tri suit underneath the wetsuit. That means you can come out of the water, remove the wetsuit, and head straight into transition without changing clothes.

More importantly, practise exactly this before race day.

A wetsuit changes your body position because the neoprene provides buoyancy, and it can feel restrictive around the shoulders if you're not used to it. A triathlon wetsuit is designed specifically to provide buoyancy while still allowing the shoulder movement required for freestyle.

Your tri suit should also be something you've tested in the water, not something you pull out of the packaging on race morning. SLS3's men's and women's triathlon suit collection is designed for use across all three disciplines, while our guide to what to wear for your first triathlon covers the broader race-day kit decisions.

The rule I give athletes is simple: race-day equipment should never be race-day equipment for the first time.

The Bottom Line

You don't need to become an open-water swimmer to prepare properly for a triathlon.

Keep building your fitness in the pool, but deliberately remove some of the conveniences the pool gives you. Practise sighting. Swim continuously. Work on breathing when your rhythm is disrupted. Learn to control your effort without constantly looking at the clock.

Then get into open water a few times before race day and gradually expose yourself to the environment.

The biggest change usually isn't physical. It's confidence.

Once the water stops feeling unfamiliar, you can concentrate on what you actually came there to do: swim smoothly, conserve energy, and get onto the bike ready to race.