As a scuba instructor I can tell you that when we deal with scuba divers we really stress that our divers - visitors - when going to any dive area in the world "leave nothing but footprints" and when it comes to what's in the water we stress "bring back nothing but memories"
North Americans are world experts at creating garbage and when I see what ends up in the oceans and how it's killing the fish I despair that we'll ever change our attitudes.