re: BP spill and some other questions...

Just watched the video and learned a lot. I wouldn't want to be the electrician who miswired those soloenoid switches on the shut off valves. But what keeps that big platform from drifting around on the surface? Why doesn't it drift around with the current and just break off the oil pipe? Surely, it must be anchored down somehow to keep it stabilized? Dumb question, perhaps, but I've always wondered how they keep the platform stabilized in one place?