This week marks the 5th anniversary of the start of one of the worst oil spills in human history.

"If you didn't know there was a spill and you went out there today, you'd never know there was ever a problem."

Cindy Caldwell is scuba diver based out of New Orleans.

Areas around New Orleans, as well as many other locations along the southern Gulf Coast of the United States, were inundated with oil after BP's oil rig "Deepwater Horizon" exploded in the Gulf of Mexico on April 20th.

Not only did it result in the deaths of 11 workers, but it also created one of the worst oil spills in U.S. history.

British Petroleum's inability to cap its deep-sea oil well after the explosion allowed millions of barrels of oil to pour into the Gulf, creating a significant ecological disaster which is still being felt today.

Despite the clear waters scuba divers are now enjoying, U.S. federal data and numerous scientific studies show that lingering problems still remain. Dolphin deaths have more than tripled.

Certian species of fish have been suffering with skin lesions.

Oil is still being found in the internal organs of others.

While most of the focus during the spill 5-years ago was on the surface of the Gulf, researchers note that not all the oil ended up going to the top.

Beth Orcutt is leading a team of researchers looking at the impact of the spill.

"Whereas a lot of the oil came up to the surface, and we saw that in all the imagery, a lot of the oil actually went down into the ocean. So, we're trying to understand what is the impact of that on the deep sea."

An estimated 10 million gallons of oil still remains on the sea floor.

Ocean Conservancy biologist Alexis Baldera says even five years on, it's still difficult to say what the long-term impact will be.

"Well, five years since the oil spill. There's still a lot of uncertainty about what we know, and I think it's important to remember that there's been a lot of studies done that are confidential. And that's just because BP and the federal government haven't settled and they haven't gone to trial and so the Natural Resources Damage Assessment is still underway."

BP published a 40-page report last month, suggesting the Gulf has mostly recovered, noting that less than 2 percent of the water and sea floor sediment samples the company took have exceeded federal toxicity levels.

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