The hardest thing to do in the back crawl turn is to find the wall.
There are a couple of ways to do this.
The first is to look for the flags across the pool and count your strokes from the flags.
The other is to count how many strokes it takes to get from one end to the other.
You need to leave space to turn on to your front and tumble, so don't count all the way to the end of the pool.
It is best to learn the front crawl tumble turn first before trying the back crawl tumble.
The two turns are almost the same - they just start and finish differently.
When you swim towards the wall on your back, you are allowed to turn on to your front to do the turn.
Practise swimming on your back and rolling on to your front.
After your tumble, you should already be on your back with your feet on the wall.
Push powerfully, stay on your back and begin your stroke.
Count your strokes and learn when to turn on to your front.
Throw your arm over your opposite shoulder to roll.
Keep your head tucked in and your arms by your side as you turn.
Don't swim on your front - only go on to your front when you start to turn.
Kick hard to get back up to the surface.