A few years ago, while working in Southern Louisiana, I was stationed at a warehouse where they did large volumes of shipping and recieving. The property of the warehouse took up about a square mile of land. One day on my lunch break I decided to stroll through the woods and find a nice spot to eat my sandwich. the woods are right next to the warehouse. I walked about 50 yards through the trees, and to my suprise I found a pond sitting there that wasnt visible from the parking lot or the building.
A couple days later I brought my fishing pole and some jigs and on my lunch break I began fishing the pond. To my suprise again, I started catching bass around 2-4lbs. I also caught some bream, warmouth, and a catfish or two, over the next several weeks. One day, after work, I went and fished the pond and caught 10-12 which I had dangling from a stringer when I walked out the woods. One of the guys from the night shift that had been working at the warehouse for several years, asked me what I was up to. I told him I found this pond in the woods and I pointed in the direction. I then held up the stringer of fish, and said "can you believe it, that pond is packed with them." He then laughed and said I wouldnt eat those if I were you." To which i replied, "why not?" He then informed me that it was a sewage treatment pond for the warehouse, and that they had quit using it about a 8 months ago, and switched to city sewer, but for many years all their sewage drained into that pond.
Haha, I didnt know what to say, so I told him I was gonna go throw them back, but I sure didnt mention the 3 meals I had eaten out of that pond over the few weeks since I had discovered it. It made me feel funny as I was driving back to my apartment, but I never got sick.