Prince Charles took a detour from his visits to various D.C. tourist spots to deliver a speech on the threat of plastic waste accumulating in the world's oceans.

The Prince of Wales delivered a 10-minute speech on the topic Wednesday afternoon to a conference of about 100 government, corporate and nonprofit leaders at the Hay-Adams Hotel across from the White House.

He cited statistics that half of all marine mammals now have plastic in their gut, and a study estimating there will be one ton of plastic in the oceans for every three tons of fish by the year 2025.

His speech emphasized recycling as one of several keys to reducing the flow of plastic into the sea.

Earlier Wednesday, Charles visited Mount Vernon, the National Archives and other sites.