To add what Mike has said, Lake Anna was originally designed to be the cooling water lagoon for the Anna Nuclear Power facility. No fears regarding safety as the Anna plant is the safest in the world. Water flowing out of the power plant can reach temperatures easily in the low 100's (it was 110 earlier this summer). As it travels from lagoon 1 to 2 to 3, it cools off considerably to where the water flowing through Dike 3 to the main body is no more than 1 or 2 degrees warmer than the other side. The "hot" side is often referred to as the "private" side because as Mike noted, access is only possible if you are a landowner on that side or a guest of one. The "cold" side or public side is accessible to any member of the public through a number of marinas and the state park. Here are some of those marinas if you ever want to get down there.
www.annapoint.com
www.highpointmarina.com
www.sturgeoncreekmarina.com
www.chistopherruncampground.com
I've been going down to the Lake for several years to boat and swim and hang with the family. Only really started fishing it this year. Don't believe the stories about the "dead sea." I've done fairly well down there. You may want to consider going with a guide. I hear Tox is supposed to be good!! For Stripers, Jim Hemby is great. He's got a link to his website at the Anna Point marina website listed above. Oh, and get a GMCO map of Lake Anna if you plan to go there. Its invaluable!
One last thing - if you do go there and need a fishing partner - ping me. I'm always looking for more fishing partners!
JC