Thanks for comments guys, well the rocks many of you are asking about, the rocks actually around 20 or 25m further down. TO be honest the jump happens so fast you can't register much, its the 30 odd seconds you spend swinging around at the bottom that are more scary, hearing the taut rope and the velcro ankle straps stretching freaked me out.
And at the bottomm you are hanging upside down, you need upright yourself and hold the rope , for someone close to a hundred kilos and out of shape, performing an upside down stomach crunch was a real struggle :S