Last Thursday, a leak from a pipeline at the Shell oil production field was spotted and cleanup vessels began to skim oil off the Gulf on Friday.
The cleanup ended Monday evening. The leak was contained after wells flowing into the pipeline were shut in.
Ian MacDonald, an oceanographer at Florida State University, said the scientists should reach the oil slick by Wednesday.
MacDonald said he flew over the spill on Sunday and found the oil about 50 miles west of where the leak happened.
"We saw porpoises in the oil, we saw balls of bait fish in the oil," he said. "From the air, you would have thought you were in the Deepwater Horizon spill."
In 2010, a BP well blew out and led to the death of 11 workers aboard the Deepwater Horizon drilling rig. For 87 days, millions of gallons of oil leaked into the Gulf in the nation's worst offshore spill.
He portrayed the spill as consisting of wide patches of rainbow sheen and long ribbons of thick oily mousse, the description of oil that has weathered.
Petty Officer Jonathan Lally with the U.S. Coast Guard said there have not been any reports of injured wildlife. The Coast Guard on Monday said skimmers had recovered more than 84,000 gallons of oily water.
MacDonald said a vessel was expected to leave Gulfport, Mississippi, on Monday with scientists who will monitor the spill and do research on what how oil affects wildlife, microbial populations and the water column. He expressed frustration that the researchers were not able to get a research vessel out to the scene faster.
"It's great that the response crew is out there, but it would be good to know what's happening to wildlife," MacDonald said.
He said the oil is moving in a westerly direction, as the U.S. Coast Guard has said. The Coast Guard has said oil is not expected to reach land. MacDonald said the oil has about 80 miles to go before it would reach the central Louisiana coast.
MacDonald and the scientists on the voyage belong to an independent research project set up after BP's 2010 catastrophic spill to study spills and the Gulf's ecosystem. The oil giant set up a $500 million fund to pay for the research.