This Surfrider Foundation campaign has been out for quite awhile, but I just saw this ad in an issue of ReadyMade magazine.
"In regions of the Pacific, plastic particles outnumber plankton six to one. Make waves. go to surfrider.org"
The rest of the ads in the campaign courtesy of google images.
(Billboard found on adverbox.)
You can see a similar ad that highlights the contents of a bird’s stomach here.