The company is using remote controlled vehicles to assess the progress off the race to limit the oil pollution in the sea off the Louisiana coast.
The dome is being lowered to the bottom of the ocean in a hugely complex operation.
It is hope the spill can be contained and the oil funnelled off safely, using the 100-tonne structure.
So far more than 30,000 barrels of oil have been collected as emergency teams work round the clock to limit the damage to wildlife and stop most of the oil hitting the shoreline.
Some of the oil has been burned but environmentalists have warned that measures so far have been inadequate. BP said in a statement: “Work continues to collect and disperse oil that has reached the surface of the sea. More than 260 vessels are being used.”