well, if you're willing to commute about 45 mins each way, you're in luck. lake murray is on the exact opposite side of town from ft. jackson!
i have no idea if there are any rentable house boats there, though. perhaps you can look at the lake murray website:
Lake Murray, South Carolina
then again, maybe i'm not thinking outside of the box -- there may be other bodies of water around, and i just don't know about them. you might want to see if lake marion is closer???