I have "adopted" about a 200 yard section of the beach near where I live and fish. I clean that up about four times a year and make sure people see me doing it so that they may get the idea. Some do get the message and comment on it, obviously others do not or I would not have to keep doing it ! It does make me feel a little better about at least doing something besides complaining. The "adopt a highway" system seems to help clean the roads where it is in place, maybe we should extend it to "adopt a beach" , "adopt a dock", etc, and commercial outfits could donate to groups like the Boy Scouts or other community groups who would actually do the cleaning. I know that once an area starts to go downhill, it usually gets bad fast. People do not hesitate to trash an area that already has a lot of trash.
If everyone just picked up one piece of trash each time they visited an area, it would make a big difference and start the trend in the right direction.