A couple of things just before the second episode of this series of Doctor Who ("Day of the Moon").
Wouldn't it be interesting if River Song turned out to be an evil villain?
In her past (the Doctor's, and our, future), she worked out that the both she and the Doctor were meeting in opposite temporal directions. And so now, before the Doctor finds out she's evil, she's playing all nice and flirting with him. And when we find out she is a villain, that's when it all changes.
Also, how did that spaceman appear and then disappear from that lake in America? No one had seen him beforehand and then he/she was just standing there. Did he, maybe, have a vortex manipulator? Who do we know with one of those?