June 8, 2010  -- A leading scientist following the BP oil spill said Monday that if the company or the government had made realistic estimates about the amounts flowing into the Gulf of Mexico, they could have had sufficient tanker space ready on the surface to hold the crude being pumped up through a make-shift collection device.

Instead, BP officials have acknowledged they may be constrained from pumping oil up too quickly because the surface ships there now can only receive only 15,000 barrels daily.

"They're groping in the dark because they've never permitted actual estimates to be made," said Ian MacDonald, a Florida State oceanography professor. "They said a dozen times on television that 5,000 barrels a day was the rate of this spill, and all their engineering was driven by that. Clearly, they were underestimating what kind of capacity they needed."

In an extensive interview with ABC News chief investigative correspondent Brian Ross, MacDonald examined underwater video from the early days of the disaster and concluded that BP had been underestimating the scope of the spill, with little objection from the U.S Coast Guard or other federal agencies. The videos were not released until more than a month into the spill, after they were sought by Sens. Bill Nelson (D-Fla.) and Barbara Boxer (D-Calif.).

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At the time, BP defended its actions, saying it had made all the video available to federal officials.

"The video has been available to the unified command from the very beginning," said Mark Proegler, a BP spokesman. "It's always been here from the beginning. They had it."

Coast Guard officials told ABC News that BP refused to allow them to release the more startling images, arguing they were proprietary. But at the time, the agency was doing little to convey to the world what the images were showing. Coast Guard Rear Admiral Mary Landry was sticking with estimates, calculated by the National Oceanic and Atmospheric Administration, which put the spill's size at about 5,000 barrels a day for several weeks. Coast Guard officials said they were focused on the response, and advised the public not to worry about just how much oil was pouring into the water.

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"I would caution you not to get fixated on an estimate of how much is out there," said Adm. Landry at a joint press conference with BP on April 30.

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