I finished surfing the other day and whilst relaxing watching the waves afterwards, looked around and nearly died. There was so much stone about that "looked" like natural hones that I got pretty excited. I don't know how to identify them but they look a bit like sandstone. Some much much finer though. I'll try and get a photo. The reality is also that I'm too new at this to even consider it right now but maybe a few years from now, assuming the stone is fine I know where I'll be able to get some rocks to start with.