Animation: The Oil Spill and How to Stop It

Here, from Al Jazeera, is a very simple little animation explaining what happened in this disastrous oil spill.


Here's what I don't get. Why is it so hard for the robot subs to turn the shutoff valve? It is just that the depth makes it hard to control the subs effectively? And if so, what good is it to have the valve in the first place if it's so far away that you can't actually use it?