Twenty-five years ago, the tanker Exxon Valdez ran aground off southern Alaska, spilling up to half a million barrels of crude oil into Prince William Sound. Thousands of kilometres of shoreline were contaminated and local wildlife was badly affected. The waters off Alaska's southern coast are clean again, but problems remain with the environment and with the health of people in the area. Al Jazeera's Daniel Lak reports from southern Alaska.