Advanced back crawl is for those who can swim quite a few lengths without having to stop for a rest.

The idea is to make each stroke longer and more powerful.

To increase your power, introduce an "S" shape into your pull.

Imagine there is a letter "S" lying on its side next to your body. The top of the letter "S" is near your feet.

Once your hand has entered the water try to move it along the shape of the letter "S".

As you push towards your feet your hand is moving down, up and down again.

This is quite difficult to achieve and will probably be easier if you find a swimming coach who can help you with this particularly complex area.

Once you get the hang of it, it will definitely improve the speed of your back crawl.

Your shoulders are very strong and can make a more powerful pull if you roll them a little bit more.