The underwater dolphin kick is often called the “fifth stroke” of swimming and for good reason. It’s the secret weapon behind the fastest swims in freestyle, butterfly, and backstroke. If you want to unlock your top speed and glide through the water like the best swimmers in the world, it’s time to break down exactly how to optimize your dolphin kick.
Why the Dolphin Kick Matters
Top swimmers move underwater faster than they do on the surface. Freestyle speeds max out around 8 km/h, but underwater, swimmers can reach up to 10 km/h. That’s why the 15-meter rule was introduced to stop swimmers from spending entire races submerged.
The dolphin kick is about more than just going fast. It’s about leverage, tempo, and mastering the flow of movement to reduce drag and increase propulsion.
Understand the Science of Speed
Think of your body like a sine wave. The wavelength, amplitude, and period (time per cycle) all affect how efficiently you move through the water.
- Wavelength: Distance between two peak points in your kick motion.
- Amplitude: Size of the kick or how far you move up and down.
- Period: Time it takes to complete one full kick cycle.
Swimmers who optimize these three variables, especially with proper kick size and rhythm, can generate a smooth, whip-like motion that accelerates them forward.
Common Mistakes Swimmers Make
Many swimmers think bigger kicks mean more speed. Not always.
- Too small: You don’t generate enough thrust.
- Too big: You create excess drag. Water is 800x denser than air.
Your goal is to find that sweet spot where you’re getting just enough undulation to move efficiently, without wasting energy or slowing down.
What Makes an Efficient Dolphin Kick?
It’s not just your legs doing the work. The best swimmers use their entire body to create a wave motion from fingertips to toes, but not equally.
The Whip Effect
The secret to speed lies at the end of the wave; your feet. Your hands move slower through the water than your feet can. That’s why the whip effect, generating the most propulsion at the end of your body is so critical.
If you’re tall, you naturally have more leverage. But even if you’re shorter, with a tight streamline and a powerful finish to your kick, you can outperform taller swimmers.
Mastering the Upkick and Downkick
There are two phases of the dolphin kick:
- Downkick: Driven by your core, hip flexors, and quads.
- Upkick: Powered by your glutes, hamstrings, and calves.
Elite swimmers generate propulsion on both ends of the kick. If you’re only strong in one direction, you’re missing out on 50% of your potential speed.
Goal: Make both sides of your kick equally effective.
Feel the Flow: Building Your Kick With Drills
Building a better dolphin kick isn’t just about kicking more. It’s about intentional training that develops your feel for the water and strengthens your full range of motion.
Flow Drill Set – 8x25s
- 25 on stomach – Arms at 11 and 1, light dolphin kicks on the surface. Focus on pressing your chest and getting your hips up.
- 25 on right side
- 25 on left side
- 25 on back – Streamline position, feel the full-body undulation.
Repeat this sequence twice to train dolphin kick in every position.
Build It Into Your Workout
Main Set – 4x75s Building Dolphin Kicks
Start each 25 with an increasing number of dolphin kicks off the wall:
- Round 1: 4 kicks
- Round 2: 5 kicks
- Round 3: 6 kicks
Add gear to change stimulus:
- Round 1: All natural
- Round 2: With fins
- Round 3: Fins + paddles
This training plan increases endurance, tests your streamline, and challenges your ability to hold form under fatigue—key to building swimming endurance and control.
Pro Tips for Faster Kicking
- Keep your arms stable – Your hands don’t need to move much.
- Focus on your feet – That’s where the real speed comes from.
- Don’t bend the knees too much – Maintain the wave, not a scissor.
- Train both upkick and downkick – For balance and full-body strength.
- Use progressive training plans – Don’t go all-in from day one.
Make the Most of Your Kick
The dolphin kick is an art and a science. It’s about learning how to generate leverage, build propulsion, and stay connected to the water. The more intentional your training, the better your results.
Whether you’re just starting out or trying to shave tenths off your 100 free, mastering your dolphin kick could be the most efficient way to swim faster without getting tired.
Want to take your swimming to the next level? Try adding these drills into your training plan, and watch your speed and confidence grow.
