Prince Charles used his trip to Washington to make an impassioned plea for action to end the dumping of plastics in the world's oceans.
The Prince of Wales called on governments, plastic producers and the public to act to end the littering of the seas which had left him "horrified".
But he remained positive, saying there was a solution to the problem caused by the "throw-away society".
Charles stressed that society had to move quicker to a circular economy - where "materials are recovered, recycled and reused instead of created, used and then thrown away".
He spoke at a day-long conference in Washington on plastics in the marine environment, attended by David Miliband, co-chair of the Global Ocean Commission.
The former foreign secretary would not be drawn on whether he had spoken to his brother, Labour leader Ed Miliband, ahead of the election but when asked about his voting habits said, "I'm very open about who I vote for."
Charles told the delegates at an exclusive Washington hotel:
Today, almost half of all marine mammals now have plastic in their gut and I know I am not the only person haunted by the tragic images of seabirds, particularly albatrosses, that have been found dead, washed up on beaches after mistaking a piece of plastic for a meal.
Charles said the solution to the problem was at hand. "Speaking as a grandfather with a new grandchild due to appear in this world in a month's time, I think we probably owe it to everyone else's grandchildren to grasp that solution."