Practice this seven-step plan for the freestyle stroke, and you’ll soon be showing off your six-pack by the pool in no time:
Swim Tall
To do this, you need to visualise slipping your entire body through a small hole in the water.  Imagine a central axis extending from the top of your head to the opposite end of the pool. Rotate your body along this axis with each stroke, stretching your leading arm (the one reaching out front) as far forward as you can.

Remember to keep the muscles in your lower back and abs taut as you power through the water. This helps keep the propulsion coming from both your arms and legs, preventing your midsection from sagging like an old first-mate's belly.

Drop an Anchor

It’s not so much about pushing your arm through the water, but more like anchoring it and pulling your body over it. Grip the water with your entire forearm and hand, holding your forearm at a right angle to your upper arm and digging in like you're gathering sand with a shovel. Remember to keep your hands broad, flat, and firm.

Put Yourself on Heavy Rotation
Each stroke begins with your leading arm having entered the water. That side of your body (the low side) should be pointing almost at the bottom of the pool. The other side of your body (the high side) should be raised, with the arm that just finished its stroke getting ready to return to the water. Power is triggered when you drive down the high side of your body, throwing your high-side arm forward along the central axis into the leading position and forcefully rotating your hips and torso. Meanwhile, your low-side arm becomes the pulling arm underwater, working with your rotating torso to provide acceleration.

Keep Your Head Down
It’s a simple trick with a major difference. Not only does this technique cut drag, it keeps your torso high, reducing strain on your neck and lower back.

Find Your Glide Path
The fewer strokes is better. Aim for a high "distance per stroke" (DPS). Try to keep yours below 20 by conserving momentum. Pull yourself over your anchor and continue to glide forward with one arm forward and the other back. You'll travel farther and faster with your legs streamlined near your axis. When you begin to slow, start the next stroke.

Drag Your Feet
Turn your feet into fins. Your legs should be taut, scissoring you through the water, while your feet remain flexible. This will help them snap at the downstroke of each kick, helping to twist your torso along the central axis. If your feet don’t flex that well, then consider getting a set of kicking fins to add flexibility.

Don't Waste Your Breath

Gasping for air every time your head nears the surface is a great way to drown, so make each breath count. Exhale all the air from your lungs while immersed, before going for a quick, full breath on the high side. Beginners will probably need to breathe after each stroke. As your endurance improves, try to breathe on alternate sides (after three strokes). This will reduce the strain on your neck and shoulders which usually results from always breathing on the same side.