Seriatopora caliendrum. It can't be a Pocillipora, as they always have verrucae (bumps) on their skeleton. This is clearly smooth.
I agree strongly with Wentreefgirl, they must have good circulation, although they seem to prefer moderate light. That said, I have seen them growing right at the water surface, not looking very attractive, but not really suffering. They were growing on the outflow pipe-end in extreme current..