Swimming is consistently underestimated as an ab workout. Most people assume you need a mat, a gym, or at minimum something solid to brace against. Water removes all of that — and that is exactly why it works.

When you're in the water, your core can't rely on ground reaction force to stabilise you. It has to generate and hold your body position against a fluid medium that pushes back from every direction. That's a higher demand on your abdominal muscles than most dry-land exercises produce, and it's continuous — not a 30-second set with rest in between.

The exercises below are sequenced to build from technique fundamentals to direct ab work to resistance-based training. All of them can be incorporated into a standard pool session. None of them require equipment beyond what's available at any lane pool.

Before targeting your abs with specific exercises, technique comes first. Not for aesthetic reasons — because poor technique actively removes ab engagement from your stroke.

The most common error: lifting your head to breathe in freestyle instead of rotating into the breathing motion. The moment you lift, your hips drop, your lower back compensates, and the rotational load that should be training your obliques disappears. The same applies to breaststroke — an exaggerated head lift creates a lumbar-heavy undulation that bypasses your anterior core entirely.

Correct technique keeps your body in a long horizontal line from head to heels. Your core is the structure that maintains that line. Every stroke becomes an ab exercise when your position is right.

Two drills that build this foundation immediately:

• Kicking on your back with arms extended overhead — forces your core to hold a flat position without the chest-buoyancy assist you get face-down
• Single-arm freestyle — one arm extended forward, one arm pulling. The asymmetry forces your obliques to prevent over-rotation on every stroke cycle

Spend ten minutes on these at the start of any ab-focused session. What you fix in technique, you don't have to compensate for with extra volume later.

Once your position is dialled in, these two exercises directly load the ab muscles you're trying to develop.

Flutter Kick

Hold the wall or the lane rope and kick your legs in a controlled, steady motion — hips at surface level, knees slightly bent on the downbeat, legs nearly straight on the upbeat. The target muscles are your lower abs and hip flexors, which are working continuously to maintain the kick rhythm. Common error: over-bending the knee and turning this into a quad exercise. Keep the movement compact and initiated from the hip, not the knee.

Protocol: 10 x 25m flutter kick, no kickboard, streamline arms, 15 seconds rest. If your hips sink in the final 10 metres, your core is fatiguing — that's your baseline.

Dolphin Kick

Face down, arms extended, body undulating from the hips in a controlled wave motion. This is the most direct ab exercise in swimming. The contraction that initiates each wave comes from your lower abdominals — your rectus abdominis, transverse abdominis, and obliques are all firing to produce and control the undulation. Unlike the flutter kick, the dolphin kick also loads your upper abs through the chest-to-hip compression phase of each wave.

Protocol: 8 x 25m dolphin kick, full recovery between sets. Short-axis strokes fatigue quickly — keep the rest intervals generous and maintain quality over volume.

If you've built a solid foundation with the drills above, adding resistance accelerates the toning process. The water itself provides resistance — but tools increase the load specifically on the muscles you're targeting.

Resistance flutter kick

Attach a resistance band to your ankles and kick against the added drag. This increases the muscular demand on every kick cycle without changing the movement pattern. Your hip flexors and lower abs work harder to maintain pace against the resistance.

Water Bicycle

Float on your back and pedal your legs in a bicycle motion — knees driving toward the chest on alternating sides. This exercise targets your rectus abdominis, obliques, and hip flexors simultaneously. The rotation of the pelvis that comes with each knee drive loads the obliques specifically. Thirty seconds of water bicycle produces more oblique activation than most mat-based exercises of equivalent duration.

Resistance Band pull-through

Anchor a band at pool edge, stand facing away, and pull through the water with one arm at a time. The bracing required to prevent your torso from rotating toward the working arm is pure oblique work.

Add one resistance exercise per session, not all three. Overloading a session with resistance work before adequate recovery leads to form breakdown — and form breakdown removes the ab engagement you're training for.

The following exercises move beyond standard lap and drill work. They can be incorporated as standalone ab circuits within a session, or used as finishers after main set work.

Treading water is the most underused ab exercise in the pool. Because your body is vertical and unsupported, your core is working to keep your head above the surface from every direction at once. The transverse abdominis — the deepest abdominal layer and the one most responsible for the 'flat stomach' effect — is continuously activated to stabilise your trunk against the water's movement.

To increase the ab demand: remove your arms. Tread with legs only — eggbeater kick or scissors kick — and cross your arms over your chest or raise them above your head. Each position shifts more load onto your core and less onto your arms and shoulders.

Protocol: 4 x 45 seconds treading, arms crossed over chest, 20 seconds rest. Progress by raising arms overhead for the final two intervals.

The standard use of a kickboard — holding it in front of you while kicking — actually reduces ab engagement by providing buoyancy assist for your chest. The more effective approach: use the kickboard vertically, held at arm's length in front of you while you tread water or perform vertical kicking in the deep end. Pushing the board down against its buoyancy forces your core to counterbalance from above.

Two kickboard exercises that specifically target the abs:

• Vertical board push-down: Standing in shoulder-deep water, hold the kickboard vertically in both hands and push it underwater, holding it submerged for five seconds before releasing. The instability of the board's resistance as it pushes back up forces your core to brace and stabilise. 3 x 10 repetitions.
  
  
• Kickboard flutter kick without resting on the board: Hold the board at arm's length rather than resting your chest on it. Your core now has to maintain your horizontal position independently. The difference in ab engagement is immediate.

This is one of the most direct lower ab exercises you can do in water. Find the pool wall or a stable ledge in deep water. Grip the edge and hang with your body fully extended downward. From that hanging position, draw both knees toward your chest in a controlled movement, then lower them back to the starting position with resistance — don't let gravity do the work.

The eccentric phase (lowering) is where most of the toning stimulus comes from. Swimmers who rush the lowering phase and let their legs drop are eliminating the most productive part of the exercise.

Protocol: 3 x 12 repetitions, controlled tempo throughout — two seconds up, three seconds down. Rest 30 seconds between sets. Progress by extending legs straight rather than drawing the knees — the lever arm increases significantly and the lower ab demand doubles.

The water bicycle — lying on your back at the surface and pedalling your legs in alternating cycles — is the primary oblique exercise in this programme. Each pedal cycle requires your torso to resist rotation toward the active leg, which loads the opposite oblique. When you add a deliberate torso twist toward the active knee, you load both obliques through the full rotation range.

The key difference from dry-land bicycle crunches: the water's resistance on your legs adds load to each pedal cycle without requiring any additional equipment. Your hip flexors and lower abs are also working continuously to maintain your body position at the surface.

Protocol: 3 x 30 seconds continuous cycling, adding the torso twist from the second set onward. 20 seconds rest between sets.

Stand in shoulder-deep water with feet hip-width apart. Bend forward from the hips until your upper body is parallel to the water surface — or as close to it as your depth allows. Then contract your abs to curl your torso upright, simultaneously driving one knee toward your chest. Lower the knee and hinge forward again for the next repetition.

The water's resistance on your torso during the upward phase increases the difficulty compared to an air equivalent. The single-leg knee drive adds a rotational component that loads the obliques. Alternate legs each repetition to train both sides evenly.

Protocol: 3 x 15 repetitions per side, continuous alternating. Keep the movement deliberate — the goal is muscular contraction, not momentum.

Stand in shoulder-deep water with feet hip-width apart. Bend forward from the hips until your upper body is parallel to the water surface — or as close to it as your depth allows. Then contract your abs to curl your torso upright, simultaneously driving one knee toward your chest. Lower the knee and hinge forward again for the next repetition.

The water's resistance on your torso during the upward phase increases the difficulty compared to an air equivalent. The single-leg knee drive adds a rotational component that loads the obliques. Alternate legs each repetition to train both sides evenly.

Protocol: 3 x 15 repetitions per side, continuous alternating. Keep the movement deliberate — the goal is muscular contraction, not momentum.

The suit you train in directly affects the quality of your ab workout. A suit that shifts during kick sets, rides up during treading water intervals, or restricts shoulder rotation during resistance drills pulls your attention away from the muscle activation you're training. That's not a small thing — core exercises in particular demand concentration on the right muscles, at the right moment.

For pool training, a performance one-piece with a secure fit, built-in shelf bra, and chlorine-resistant fabric is the right tool. The Yemaya One Piece is built specifically for lap and drill work — it stays in place through high-kick sets, water bicycle intervals, and wall grab repetitions without adjustment. The full back provides the freedom of movement that restricted swimwear removes from exercises like resistance pull-throughs and dolphin kick.

If you train in open water as well as the pool — or you're extending your season into cooler water (16–20°C) where longer sessions are only comfortable in neoprene — the Springsuit Boyleg solves the coverage and thermal problem simultaneously. The boyleg cut was designed specifically to address the 'rides up during swimming' issue that's common in standard-cut suits. In open water, where you're doing longer flutter kick sets and treading water without pool walls to rest on, a suit that stays put matters.

Browse the full performance swim collection for suits built for training, not just wearing to the pool.

The only thing between a woman and the water should be clean.

Use this 45-minute session structure to apply everything above in a single, progressive workout. Suitable for intermediate swimmers training in a lane pool.

Warm-Up (10 minutes)

• 400m easy freestyle — focus on hip rotation, not speed. Count the degrees of torso rotation on each breath stroke.
• 4 x 25m single-arm freestyle, alternating arms every 25m, 20 seconds rest

Main Set (25 minutes)

• 10 x 25m flutter kick, no kickboard, streamline position, 15 seconds rest
• 8 x 25m dolphin kick, full recovery between sets
• 3 x 45 seconds treading water (arms crossed over chest), 20 seconds rest
• 3 x 12 wall grab leg raises, controlled tempo, 30 seconds rest
• 3 x 30 seconds water bicycle with torso twist, 20 seconds rest
• 4 x 30 seconds high knees in shoulder-deep water, 30 seconds rest

Cool-Down (10 minutes)

• 200m easy backstroke — focus on maintaining a flat hip position throughout
• 4 x 25m sculling, slow and deliberate

Total volume: approximately 2,100 metres. Compress the main set intervals if you're earlier in your training progression, or add resistance band work to two of the kick sets if you're looking for additional load.