There’s a quiet truth in ocean swimming that often gets overlooked: your arms might pull you forward, but it’s your core that holds everything together.

In the pool, it’s easy to get away with a loose body line. The water is flat, predictable, and forgiving. But step into the ocean, and suddenly every weakness is exposed. Chop, swell, currents, and fatigue all test your ability to stay long, stable, and efficient through the water.

That’s where a strong, connected core becomes your greatest asset.

Why core strength matters in the ocean

In open water, your core isn’t just about ‘abs’, it’s your entire trunk: hips, lower back, obliques, and deep stabilising muscles. Together, they control your body position and transfer power from your stroke.

A strong core helps you:

• Hold a streamlined body position in messy conditions
• Reduce drag by keeping your hips high
• Transfer power efficiently from your catch to your kick
• Stay balanced when breathing in chop
• Maintain rhythm when fatigue sets in

Without it, you’ll feel it quickly, legs dropping, stroke shortening, and energy draining faster than it should.

How the pool becomes your core training ground

The pool is the perfect place to build core strength because you can isolate movements, control conditions, and focus on technique without the chaos of the ocean.

Instead of thinking about ‘doing core work,’ think about swimming in a way that demands core engagement.

1. Kick sets that build stability

Kicking isn’t just about legs; it’s one of the best ways to train your core.

Try this:

• 6 x 50m freestyle kick
• Focus on tight glutes, engaged abs, and minimal knee bend
• Keep your hips high and body flat

Progression:

• Kick on your side (one arm extended)
• Kick without a board, arms streamlined overhead

Why it works: Your core has to stabilise your body to stop you from sinking or snaking through the water.

2. Pull buoy done right (not lazy swimming)

The pull buoy often gets used as a ‘rest tool,’ but it’s actually a powerful core drill when used properly.

Try this:

• 4 x 100m pull buoy, no paddles
• Lightly engage your core to hold alignment, don’t rely on the buoy
• Keep your kick still and controlled

Add a challenge:

• Use a band with the buoy, but be careful not to overload the shoulders

Why it works: It forces your core to keep your body straight without the help of a kick.

3. Single-arm freestyle for rotation control

Ocean swimming demands controlled rotation, especially when breathing in waves.

Try this:

• 6 x 50m single-arm freestyle (3 right arm, 3 left arm)
• Non-stroking arm stays by your side
• Focus on rotating through the hips, not just the shoulders

Why it works: It trains your core to drive rotation and maintain balance, just like when sighting or breathing in chop.

4. Sculling for connection and feel

Sculling looks simple, but it lights up your core when done correctly.

Try this:

• 4 x 50m scull (front, mid, or catch position)
• Keep your body long and still
• Engage your core to prevent your legs from sinking

Why it works: You’re forced to stabilise your body while generating propulsion with minimal movement.

5. Streamline kick

This is one of the most underrated core exercises in swimming and helps your streamline at the same time. 

Try this:

• Push off the wall in a tight streamline (arms locked overhead)
• Kick for 25 – 50m without breaking position

Focus on:

• Squeezing your ears with your arms
• Tight core and glutes
• No arching through the lower back

Why it works: If your core switches off, your body line falls apart instantly.

Bringing it into the ocean

The goal isn’t just to have a ‘strong core’ in the gym or pool, it’s to translate that strength into better swimming when conditions aren’t perfect.

When your core is switched on, you’ll notice:

• You ride over waves instead of being knocked around
• Your stroke stays long even when you’re tired
• Breathing feels more controlled in chop
• You hold your line better when sighting
• You waste less energy fighting the water
• Keep It Simple, Keep It Consistent

You don’t need a separate core session to become a stronger ocean swimmer. Just be intentional with how you swim your sets.

Add one or two of these drills into each session, focus on body position, and stay connected through your stroke.

Because in the ocean, strength isn’t about muscling through the water.

It’s about holding yourself together when the water tries to pull you apart.