all right. welcome back. now a story about the nation s all right. welcome back. now a story about the nation s lakes being invaded by a slimy enemy. there s nothing nice about this stuff. it is smelly, and it looks bad. all that and it s dangerous. abc s jim avila went to wisconsin, put on some waders, and got into the story literally. reporter: it s an assault on nearly all the senses. a living, breathing, growing, toxic organism known as blue/green algae, and it is worse this month. that is very much alive. reporter: gosh, the smell is bad. caking america s lakes so thick, the swirling slime can be seen in photos from space. people that used to be here, after a couple of years said we can t handle it anymore and left. reporter: tom runs the marina in lake petenwell, wisconsin, or tries to. nobody will swim or boat in it.