This is for swimmers who are now able to complete at least one length of butterfly without stopping.

The dolphin-like motion of the body through the water is known as undulation.

Keep the hips moving up and down with the kick and stretch the arms forward as you put them into the water.

Video masterclass: Steve Parry's butterfly guide

This will stop you diving too deep. Try and keep the dolphin motion going but keep it close to the surface.

You should be able to keep a good regular kicking action going all of the time.

Now try to put some extra power into it by whipping the legs downwards each time you kick.

Each kick should finish with the legs straight.

Using the keyhole pull described in the intermediate butterly, bend the elbows at the start of the stroke and keep them close to the surface.

Use your chest and shoulders to press the hands to the feet. Keep the arms moving all the time.

If you can, breathe every two strokes to keep your body streamlined.

Try keeping your head down for one arm pull and then breathing on the next arm pull. Keep this going for as long as you can.

Every time you pull once with your arms, you should kick twice with your legs.

This means that your legs will keep moving.

Try Steve Parry's butterfly challenge

Finally, do not let your arms stop after they enter the water.