The park is very nice, the proprieter friendly. I have no doubt that the folks who are experiencing the 50' vis are telling the truth, and have heard trusted friends speak of memories of being at Athens when the vis was that way. My only trip to Athens was a few years ago, in June or July. It was the middle of the week (Wed., I think) and there were only a handful of divers across the lake from my husband, daughter, and me. The water looked so amazing from the dock- then when we got in, there seemed to be a white particulate in the water that really hurt the vis. Was this an algae bloom? I'm not sure, but it was very disorienting as you finned along- it reminded me of being in the old "Asteroids" game, and definitely caused the vis to be poor. There were some very cool items sunk- we found a schoolbus and I think a VW bug. My frustration came when my daughter and I (both bottle-blondes) came out of our beanies/doo-rags, after diving. The realization that both of us were suddenly sporting new green locks on our heads was pretty horrifying, to say the least. When we got to the (very nice, with hot water) showers, one of the workers was waiting with "green-out" shampoo (!!) Okay- mixed feelings- the shampoo was much appreciated (although it didn't completely remove the green) but evidently they knew our hair was going to turn green. I would have appreciated a warning. We could have wet our heads PRIOR to getting in the water, and put on protective conditioner. Then, the porosity of our hair wouldn't have soaked so much of whatever it is in the water that turned our hair green. Whatever the reason, be it high/low pH, I dunno. I'm sure I'm not going to be very popular with Calvin after this post, but people deserve to know that this might happen, then they can take proper precautions before diving. There are many positive things about Athens, and I would recommend it as a local dive spot.
By the way, if your blonde hair (whether natural blonde or color-treated) turns green from this type of reaction, or swimming pools, mix baking soda with your shampoo. After a few days of washing with this mix, you should be back to normal. ;-)