these oil rigs have a balancing system that transfers water
between the legs of the platform to try and keep the rig level
in heavy seas.
if someone opened a watertight access and water flowed in
the access this might be the reason that the platform tilted.
then if the automatic balancing system transfered water in the
other legs to compensate for the tilt , well it wouldnt take
long to sink.
I just thought about this , there may have also been oil pouring into one of the legs as it tilted.
anyway , Im not exactly sure how it works and I might be wrong.
still the fire crews should not be at fault.
but the designers of the vessel and the safety training of the vessels crew.
and it could be that the crew could not get to the access
because of the water being pumped onto the deck.
from the looks of the videos trying to do anything on that rig , even trying to catch a breath of air would be
hard to do.
the eleven who are missing must have been trying there best to save the vessel from sinking , they might have even
been down in a leg trying to fix or start some pump or something as it filled with water and possibly even oil.
they must be heros.
the deepwater horizon specs a forum with some great pictures of the rig before and after.
close up shots of the rig before it sunk 
