A sea otter shares the waters of Alaska’s foggy Prince William Sound with a spill-containment vessel nearly a decade after the Exxon Valdez ran aground and fouled these pristine waters with 11 million gallons (40 million liters) of crude oil. Intense clean-up efforts after the disaster lasted more than four years.

Now, evidence of the spill is hard to detect. But some beaches still have Valdez oil buried just below the surface. And scientists say some animal species, including sea otters, harbor seals, harlequin ducks, and herring, have yet to recover from the spill’s negative effects.

(Photograph from "In the Wake of the Spill: Ten Years After Exxon Valdez," March 1999, National Geographic magazine)